TransDigm (TDG) 10-K 12 Nov 20 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2020	Oct. 28, 2020	Mar. 31, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-32833
Entity Registrant Name	TransDigm Group Incorporated
Entity Central Index Key	0001260221
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	41-2101738
Entity Address, Address Line One	1301 East 9th Street,
Entity Address, Address Line Two	Suite 3000,
Entity Address, City or Town	Cleveland,
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	44114
City Area Code	216
Local Phone Number	706-2960
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	TDG
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 17,842,940,279
Entity Common Stock, Shares Outstanding		54,435,882
Documents Incorporated by Reference	Certain sections of the registrant’s definitive Proxy Statement to be filed in connection with its 2021 Annual Meeting of Shareholders are incorporated by reference into Part III of this Annual Report on Form 10-K.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 4,717	$ 1,467
Trade accounts receivable—Net	720	1,068
Inventories—Net	1,283	1,233
Assets held-for-sale	0	962
Prepaid expenses and other	240	135
Total current assets	6,960	4,865
PROPERTY, PLANT AND EQUIPMENT—NET	752	757
GOODWILL	7,889	7,820
OTHER INTANGIBLE ASSETS—NET	2,610	2,744
DEFERRED INCOME TAXES	17	0
OTHER	167	69
TOTAL ASSETS	18,395	16,255
CURRENT LIABILITIES:
Current portion of long-term debt	276	80
Short-term borrowings—trade receivable securitization facility	349	350
Accounts payable	218	276
Accrued liabilities	773	675
Liabilities held-for-sale	0	157
Total current liabilities	1,616	1,538
LONG-TERM DEBT	19,384	16,469
Deferred Income Tax Liabilities, Net	430	441
OTHER NON-CURRENT LIABILITIES	933	691
Total liabilities	22,363	19,139
TD GROUP STOCKHOLDERS’ DEFICIT:
Common stock - $.01 par value; authorized 224,400,000 shares; issued 58,612,028 and 57,623,311 at September 30, 2020 and September 30, 2019, respectively	$ 1	$ 1
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common stock, shares authorized	224,400,000	224,400,000
Common stock, shares issued	58,612,028	57,623,311
Additional paid-in capital	$ 1,581	$ 1,379
Accumulated deficit	(4,359)	(3,120)
Accumulated other comprehensive loss	$ (401)	$ (379)
Treasury stock, shares	(4,198,226)	(4,161,326)
Treasury stock, at cost; 4,198,226 and 4,161,326 shares at September 30, 2020 and September 30, 2019, respectively	$ (794)	$ (775)
Total TD Group stockholders’ deficit	(3,972)	(2,894)
Non-controlling Interests	4	10
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(3,968)	(2,884)
TOTAL LIABILITIES AND STOCKHOLDERS’ DEFICIT	$ 18,395	$ 16,255

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2020	Sep. 30, 2019
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	224,400,000	224,400,000
Common stock, shares issued	58,612,028	57,623,311
Treasury stock, shares	4,198,226	4,161,326

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
NET SALES	$ 5,103	$ 5,223	$ 3,811
COST OF SALES	2,456	2,414	1,634
GROSS PROFIT	2,647	2,809	2,177
SELLING AND ADMINISTRATIVE EXPENSES	727	748	450
AMORTIZATION OF INTANGIBLE ASSETS	169	135	72
INCOME FROM OPERATIONS	1,751	1,926	1,655
INTEREST EXPENSE—NET	1,029	859	663
REFINANCING COSTS	28	3	6
OTHER (INCOME) EXPENSE	(46)	1	0
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	740	1,063	986
INCOME TAX PROVISION	87	222	24
INCOME FROM CONTINUING OPERATIONS	653	841	962
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAX	47	51	(5)
Net income	700	892	957
Less: Net income attributable to noncontrolling interests	(1)	(2)	0
Net income attributable to TD Group	699	890	957
NET INCOME APPLICABLE TO TD GROUP COMMON STOCKHOLDERS	$ 514	$ 779	$ 901
Earnings per share attributable to TD Group common stockholders:
Earnings per share from continuing operations—basic and diluted	$ 8.14	$ 12.94	$ 16.28
Earnings (Loss) per share from discontinued operations—basic and diluted	0.82	0.90	(0.08)
Earnings per share	8.96	13.84	16.20
Cash dividends paid per common share	$ 32.50	$ 30	$ 0
Weighted-average shares outstanding:
Basic and diluted	57.3	56.3	55.6

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Net income	$ 700	$ 892	$ 957
Less: Net income attributable to noncontrolling interests	(1)	(2)	0
Net income attributable to TD Group	699	890	957
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments, net of tax	76	(115)	(10)
Unrealized (loss) gain on derivatives	(130)	(239)	94
Pensions and other postretirement benefits	32	(29)	5
Other comprehensive (loss) income, net of tax, attributable to TD Group	(22)	(383)	89
TOTAL COMPREHENSIVE INCOME ATTRIBUTABLE TO TD GROUP	$ 677	$ 507	$ 1,046

Consolidated Statement of Chang

Consolidated Statement of Changes in Stockholders' Deficit - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Noncontrolling Interest [Member]	Accumulated Other Comprehensive (Loss) Income	Treasury Stock
Non-controlling Interests					$ 0
Treasury Stock, Shares							(4,159,207)
Common Stock, Shares, Issued at Sep. 30, 2017		56,093,659
TD Group Stockholders at Sep. 30, 2017	$ (2,951)	$ 1	$ 1,095	$ (3,187)		$ (85)	$ (775)
BALANCE at Sep. 30, 2018		$ 1	1,209	(2,247)		4	$ (775)
Accrued unvested dividend equivalents and other	(17)			(17)
Compensation expense recognized for employee stock options	56		56
Exercise of employee stock options	58		58
Exercise of employee stock options		800,955					(2,119)
Common stock issued		1,072
Net income	957
Net income attributable to TD Group	957			957
Unrealized loss on derivatives, net of tax	94					94
Foreign currency translation adjustments, net of tax	(10)					(10)
Pensions and other postretirement benefits adjustments, net of tax	5					5
Non-controlling Interests					0
Treasury Stock, Shares							(4,161,326)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(1,808)
Noncontrolling interests assumed related to acquisitions	8				8
Common Stock, Shares, Issued at Sep. 30, 2018		56,895,686
BALANCE at Sep. 30, 2019	(2,894)	$ 1	1,379	(3,120)		(379)	$ (775)
Dividends paid	(1,688)			(1,688)
Accrued unvested dividend equivalents and other	(80)			(80)
Compensation expense recognized for employee stock options	88		88
Exercise of employee stock options	82		82
Exercise of employee stock options		726,750
Common stock issued		875
Net income	892
Net income attributable to TD Group	890
Net Income (Loss) from Noncontrolling Interest					2
Unrealized loss on derivatives, net of tax	(239)					(237)
Foreign currency translation adjustments, net of tax	(115)					(115)
Other Comprehensive Loss, Derivatives Qualifying as Hedges	(237)
Pensions and other postretirement benefits adjustments, net of tax	(29)					(29)
Cumulative Effect on Retained Earnings, Net | Accounting Standards Update 2014-09 [Member]	3			3
Cumulative Effect on Retained Earnings, Net | Accounting Standards Update 2018-02 [Member]	0			2
Non-controlling Interests	$ 10				10
Treasury Stock, Shares	4,161,326						(4,161,326)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (2,884)
Noncontrolling interests attributable to divestiture	$ (6)				(6)
Common Stock, Shares, Issued at Sep. 30, 2019	57,623,311	57,623,311
BALANCE at Sep. 30, 2020	$ (3,972)	$ 1	1,581	(4,359)		(401)	$ (794)
Dividends paid	(1,864)			(1,864)
Accrued unvested dividend equivalents and other	(74)			$ (74)
Compensation expense recognized for employee stock options	86		86
Exercise of employee stock options	116		$ 116
Exercise of employee stock options		988,717
Treasury stock purchased	(19)						$ (19)
Treasury stock purchased							(36,900)
Net income	700
Net income attributable to TD Group	699
Unrealized loss on derivatives, net of tax	(130)					(130)
Foreign currency translation adjustments, net of tax	76					76
Pensions and other postretirement benefits adjustments, net of tax	32					$ 32
Non-controlling Interests	$ 4				$ 4
Treasury Stock, Shares	4,198,226						(4,198,226)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (3,968)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
OPERATING ACTIVITIES:
Net income	$ 700	$ 892	$ 957
Net (income) loss from discontinued operations	(47)	(51)	5
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	114	91	57
Amortization of intangible assets	169	135	72
Amortization of debt issuance costs, original issue discount and premium	33	28	22
Amortization of inventory step-up	0	77	7
Amortization of loss contract reserves	36	38	(10)
Refinancing costs	28	3	6
Non-cash stock compensation	92.7	93.4	58.5
Deferred income taxes	24	0	(151)
Changes in assets/liabilities, net of effects from acquisitions and sales of businesses:
Trade accounts receivable	352	(82)	(44)
Inventories	(62)	(36)	(18)
Income taxes (receivable) or payable	(144)	(3)	36
Other assets	(16)	(27)	(5)
Accounts payable	(62)	(1)	18
Accrued interest	85	(4)	14
Accrued and other liabilities	(18)	(62)	(2)
Net cash provided by operating activities	1,213	1,015	1,022
INVESTING ACTIVITIES:
Capital expenditures	(105)	(102)	(73)
Payments made in connection with acquisitions	0	(3,976)	(668)
Proceeds in connection with the sale of discontinued operations	904	189	57
Net cash provided by (used in) investing activities	799	(3,889)	(684)
FINANCING ACTIVITIES:
Proceeds from exercise of stock options	116	82	58
Dividends and dividend equivalent payments	(1,928)	(1,712)	(56)
Treasury stock purchases	(19)	0	0
Proceeds from revolving credit facility	200	0	0
Proceeds from 5.50% senior subordinated notes due 2027, net	0	0	12,779
Proceeds from term loans, net	0	544	490
Repayment on term loans	(75)	(77)	(12,174)
Repayments of Senior Debt	0	550	0
Redemption of senior subordinated notes due 2022, net	1,167	0	0
Proceeds from 7.50% senior subordinated notes due 2027, net	2,625	0	0
Proceeds from 6.25% senior secured notes due 2026, net	399	3,936	0
Proceeds from 8.00% senior secured notes due 2025, net	1,090	0	0
Proceeds from trade receivable securitization facility, net	0	49	0
Financing costs and other, net	(11)	(1)	(11)
Net cash provided by financing activities	1,230	2,271	1,086
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	8	(3)	(2)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	3,250	(606)	1,422
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	1,467	2,073	651
CASH AND CASH EQUIVALENTS, END OF PERIOD	4,717	1,467	2,073
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid during the period for interest	923	878	635
Cash paid during the period for income taxes, net of refunds	$ 223	$ 215	$ 129

DESCRIPTION OF THE BUSINESS AND

DESCRIPTION OF THE BUSINESS AND IMPACT OF COVID-19 PANDEMIC	12 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
DESCRIPTION OF THE BUSINESS AND IMPACT OF COVID-19	DESCRIPTION OF THE BUSINESS AND IMPACT OF COVID-19 PANDEMIC Description of the Business – TD Group, through its wholly-owned subsidiary, TransDigm Inc., is a leading global designer, producer and supplier of highly engineered aircraft components for use on nearly every commercial and military aircraft in service today. TransDigm Inc., along with TransDigm Inc.’s direct and indirect wholly-owned operating subsidiaries (collectively, with TD Group, the “Company” or “TransDigm”), offers a broad range of proprietary aerospace products. TD Group has no significant assets or operations other than its 100% ownership of TransDigm Inc. TD Group’s common stock is listed on the New York Stock Exchange, or the NYSE, under the trading symbol “TDG.” TransDigm's major product offerings, substantially all of which are ultimately provided to end-users in the aerospace industry, include mechanical/electro-mechanical actuators and controls, ignition systems and engine technology, specialized pumps and valves, power conditioning devices, specialized AC/DC electric motors and generators, batteries and chargers, engineered latching and locking devices, engineered rods, engineered connectors and elastomer sealing solutions, databus and power controls, cockpit security components and systems, specialized and advanced cockpit displays, aircraft audio systems, specialized lavatory components, seat belts and safety restraints, engineered and customized interior surfaces and related components, advanced sensor products, switches and relay panels, thermal protection and insulation, lighting and control technology, parachutes, high performance hoists, winches and lifting devices, and cargo loading, handling and delivery systems. Impact of COVID-19 Pandemic – In December 2019, COVID-19 surfaced in Wuhan, China, and has since spread to other countries, including the United States. In March 2020, the World Health Organization characterized COVID-19 as a pandemic. The pandemic has resulted in governments around the world implementing increasingly stringent measures to help control the spread of the virus, including quarantines, “shelter in place” and “stay at home” orders, travel restrictions, business curtailments and other measures. In addition, governments and central banks in several parts of the world have enacted fiscal and monetary stimulus measures to counteract the impacts of COVID-19. The commercial aerospace industry, in particular, has been significantly disrupted, both domestically and internationally. Employee Safety and Cost Mitigation Measures The Company took immediate and aggressive action to minimize the spread of COVID-19 in our workplaces and reduce costs. Since the early days of the pandemic, we have been following guidance from the World Health Organization and the U.S. Center for Disease Control to protect employees and prevent the spread of the virus within all of our facilities globally. Some of the actions implemented include: flexible work-from-home scheduling; alternate shift schedules; pre-shift temperature screenings, where allowed by law; social distancing; appropriate personal protective equipment; facility deep cleaning; and paid quarantine time for impacted employees. Material actions to reduce costs included: (1) reducing its workforce to align operations with customer demand; (2) implementing unpaid furloughs and salary reductions; and (3) delaying non-essential capital projects and minimizing discretionary spending. For the fiscal year ended September 30, 2020, COVID-19 restructuring costs incurred were approximately $46 million, of which $37 million was recorded in cost of sales and $9 million was recorded in selling and administrative expenses on the consolidated statements of income. These were costs related to the Company's actions to reduce its workforce to align with customer demand. Additionally, the Company incurred approximately $5 million in incremental costs related to the pandemic that are not expected to recur once the pandemic has subsided and are clearly separable from normal operations (e.g., additional cleaning and disinfecting of facilities by contractors above and beyond normal requirements, personal protective equipment, etc.). As of September 30, 2020 the restructuring accrual associated with the costs incurred in response to the COVID-19 pandemic was approximately $13 million. This accrual is recorded as a component of accrued liabilities on the consolidated balance sheet. The Company expects to incur and pay additional restructuring costs during fiscal 2021 related to the COVID-19 pandemic though at a reduced level in comparison to fiscal 2020. The Company continues to analyze its cost structure and may implement additional cost reduction measures as necessary due to the ongoing business challenges resulting from the COVID-19 pandemic. Impairment Testing U.S. GAAP requires that both indefinite-lived intangible assets and goodwill are tested for impairment annually and more frequently if events or changes in circumstances indicate that it is more likely than not (i.e., a likelihood greater than 50%) that the intangible asset or the reporting unit is impaired. During interim periods, ASC 350 requires companies to focus on those events and circumstances that affect significant inputs used to determine the fair value of the asset, asset group or reporting unit to determine whether an interim quantitative impairment test is required. Given the adverse global economic and market conditions attributable to the COVID-19 pandemic, particularly as it pertains to the commercial sector of the aerospace and defense industry, the Company determined that an interim impairment evaluation of goodwill and indefinite-lived intangible assets was necessary as of the second quarter of fiscal 2020 for certain reporting units in which it was concluded a potential impairment existed. Interim Impairment Testing —For the identified reporting units, a Step 1 impairment test was performed using an income approach based on management’s determination of the prospective financial information with consideration given to the existing uncertainty in the global economy and aerospace and defense industry, particularly the commercial sector. Management also included projected declines and subsequent recovery in commercial OEM and aftermarket as a percentage of sales based on available industry data. The Company utilized a third party valuation firm to assist in the determination of the weighted average cost of capital. The results of this test indicated the fair value exceeded carrying value for all reporting units tested. As a result of the interim impairment testing performed as of March 28, 2020, no indefinite-lived intangible assets or goodwill was determined to be impaired. Management updated our assessment during the third quarter of fiscal 2020 and validated that the assumptions used in the analyses performed as of March 28, 2020 and the resulting conclusions remained appropriate as of June 27, 2020. Annual Impairment Testing —The Company performed its annual impairment test for goodwill and intangible assets as of the first day of the fourth quarter. The Company first assessed certain qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit or indefinite lived intangible assets is less than its carrying amount, and whether it is therefore necessary to perform the quantitative impairment test. Given the adverse global economic and market conditions attributable to the COVID-19 pandemic, particularly as it pertains to the commercial sector of the aerospace and defense industry, the Company used a similar approach to the interim impairment testing performed. For the identified reporting units, the Company performed a Step 1 impairment test using an income approach based on management’s determination of the prospective financial information with consideration given to the existing uncertainty in the global economy and aerospace and defense industry, particularly the commercial sector. Management also included projected declines and subsequent recovery in commercial OEM and aftermarket as a percentage of sales based on available industry data. The Company utilized a third party valuation firm to assist in the determination of the weighted average cost of capital. The Company performed a sensitivity analysis on the discount rate, which is a significant assumption in the calculation of fair values. With a one percentage point increase in the discount rate, all of the reporting units would continue to have fair values in excess of their respective carrying values. As a result of the impairment testing performed as of the first day of the fourth quarter, no indefinite-lived intangible assets or goodwill was determined to be impaired. As economic and market conditions have not changed significantly since the first day of the fourth quarter, this conclusion remains appropriate as of September 30, 2020. CARES Act

ACQUISITIONS

ACQUISITIONS	12 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
ACQUISITIONS AND DIVESTITURES	ACQUISITIONS AND DIVESTITURES During the fiscal year ended September 30, 2019, the Company completed the acquisitions of Esterline and substantially all of the assets and technical data rights of the Stormscope product line from L3Harris Technologies, Inc. ("Stormscope") and NavCom Defense Electronics ("NavCom"). The Company accounted for the acquisitions using the acquisition method and included the results of operations of the acquisitions in its consolidated financial statements from the effective date of each acquisition. The acquisitions strengthen and expand the Company’s position to design, produce and supply highly engineered proprietary aerospace components in niche markets with significant aftermarket content and provide opportunities to create value through the application of our three core value-driven operating strategies (obtaining profitable new business, improving our cost structure, and providing highly engineered value-added products to customers). The purchase price paid for each acquisition reflects the current earnings before interest, taxes, depreciation and amortization (“EBITDA”) and cash flows, as well as the future EBITDA and cash flows expected to be generated by the business, which are driven in most cases by the recurring aftermarket consumption over the life of a particular aircraft, estimated to be approximately 25 to 30 years. Acquisitions Esterline – On March 14, 2019, TransDigm completed the acquisition of all the outstanding stock of Esterline for $122.50 per share in cash, plus the repayment of Esterline debt. The purchase price, net of cash acquired of approximately $398.2 million, totaled approximately $3,923.9 million. Of the $3,923.9 million purchase price, $3,536.3 million was paid at closing and the remaining $387.6 million was classified as restricted cash for the redemption of Esterline’s outstanding senior notes due 2023 (the "2023 Notes"). The 2023 Notes were redeemed on April 15, 2019. Esterline, through its subsidiaries, was an industry leader in specialized manufacturing for the aerospace and defense industry primarily within three core disciplines: advanced materials, avionics and controls and sensors and systems. The acquisition of Esterline expands TransDigm's platform of proprietary and sole source content for the aerospace and defense industry. TransDigm evaluated the strategic fit and description of each Esterline reporting unit to determine the appropriate business segment for the reporting unit. Each Esterline reporting unit is included in one of TransDigm's segments: Power and Control, Airframe, or Non-aviation. Refer to Note 17, "Segments," for additional information about the Company's segments. The total purchase price of Esterline was allocated to the underlying assets acquired and liabilities assumed based upon the respective fair value at the date of acquisition. To the extent the purchase price exceeded the fair value of the net identifiable tangible and intangible assets acquired, such excess was allocated to goodwill. Allocations were based on the acquisition method of accounting and third-party valuation appraisals. The allocation of the fair value of the assets acquired and liabilities assumed in the Esterline acquisition as of the acquisition date of March 14, 2019 is summarized in the table below (in millions). Assets acquired, excluding cash: Trade accounts receivable $ 384 Inventories 583 Prepaid expenses and other current assets 423 Property, plant, and equipment 469 Other intangible assets 1,301 Goodwill 2,256 Other 20 Total assets acquired, excluding cash 5,436 Liabilities assumed: Accounts payable 146 Other current liabilities 751 Other noncurrent liabilities 615 Total liabilities assumed 1,512 Net assets acquired $ 3,924 Of the approximately $2.3 billion of goodwill recognized for the acquisition, approximately $25.6 million is deductible for tax purposes. Also, of the approximately $1.3 billion of other intangible assets recognized for the acquisition, approximately $48.9 million is deductible for tax purposes. In connection with the Esterline acquisition, we acquired existing long-term contracts with customers that were incurring negative gross margins as of the date of acquisition. Based on our review of these contracts, we concluded that the terms of certain of these loss-making contracts were unfavorable when compared to market terms as of the acquisition date. As a result, we recognized loss contract reserves of $267.9 million as of the acquisition date based on the present value of the difference between the contractual cash flows of the existing long-term contracts and the estimated cash flows had the contracts been executed at market terms as of the acquisition date. These adjustments applied only to contracts generating a negative margin as of the date of acquisition. As of September 30, 2019, we have reclassified $9.3 million in loss contract reserves to liabilities held-for-sale, as it pertains to Souriau-Sunbank. Significant assumptions used to determine the fair value of the loss contract reserves using the discounted cash flow model include discount rates, forecasted quantities of products to be sold under the long-term contracts and market prices for respective products. These were forward looking assumptions and could be affected by future economic and market conditions. The loss contract reserves are amortized and recorded as an offset to cost of sales over the life of the contracts as actual sales occur under the long-term contracts. Approximately $29.5 million and $27.3 million was amortized and recorded as an offset to cost of sales in the consolidated statements of income for the fiscal years ended September 30, 2020 and 2019, respectively. Total loss contract reserves related to the Esterline acquisition were $201.3 million and $231.8 million at September 30, 2020 and 2019, respectively of which $31.9 million and $60.0 million is classified in accrued liabilities and $169.4 million and $171.8 million is classified in other non-current liabilities in the consolidated balance sheets at September 30, 2020 and 2019, respectively. Esterline acquisition costs were expensed as incurred and totaled $26.9 million and $85.1 million for the the fiscal years ended September 30, 2020 and September 30, 2019, respectively. Skandia – On July 13, 2018, the Company acquired all of the outstanding stock of Skandia for a total purchase price of approximately $84.3 million, which is net of a $0.2 million working capital settlement paid in the fourth quarter of fiscal 2018. Skandia provides highly engineered seating foam, foam fabrication, flammability testing and acoustic solutions for the business jet market. Skandia is included as a product line within an existing reporting unit in TransDigm's Airframe segment. No goodwill recognized for the acquisition is deductible for tax purposes. Extant – On April 24, 2018, the Company acquired all of the outstanding stock of Extant for a total purchase price of approximately $533.1 million in cash, which is net of a $0.2 million working capital settlement received in the third quarter of fiscal 2018. Extant provides a broad range of proprietary aftermarket products and repair and overhaul services to the aerospace and defense end markets. Extant is included in TransDigm's Power and Control segment. Prior to the Company's acquisition of Extant, Extant was owned by an equity fund sponsored by Warburg Pincus LLC. Michael Graff, a director of TransDigm, is a managing director of Warburg Pincus LLC and was chairman of the board of Extant. Robert Henderson, Vice Chairman of TransDigm, was also on the board of Extant and owned less than 2% of Extant on a fully diluted basis. In addition, Mr. Graff, Mr. W. Nicholas Howley, TransDigm's Executive Chairman, Mr. Douglas Peacock, then a director of TransDigm, and Mr. David Barr, a director of TransDigm, each had minority interests of less than 1% in the Warburg Pincus LLC fund that owned Extant. The total purchase price of Extant was allocated to the underlying assets acquired and liabilities assumed based upon the fair values at the date of acquisition. To the extent the purchase price exceeded the fair value of the net identifiable tangible and intangible assets acquired, such excess was allocated to goodwill. Approximately $62.5 million of the $105.0 million other intangible assets recognized for the acquisition is deductible for tax purposes over 15 years. Of the $407.0 million of goodwill recognized for the acquisition, approximately $12.4 million is deductible for tax purposes. Extant Acquisitions - On August 30, 2019, the Company's Extant subsidiary completed the acquisition of substantially all of the assets and technical data rights of the Stormscope product line from L3Harris Technologies, Inc. for approximately $20 million in cash. Stormscope is a lightning detection system for the general aviation market. Stormscope is included as a product line of Extant, which is included in TransDigm's Power and Control segment. Approximately $11.1 million of goodwill recognized for the acquisition and approximately $7.5 million of other intangible assets recognized for the acquisition is deductible for tax purposes over 15 years. On October 1, 2018, the Company's Extant subsidiary completed the acquisition of substantially all of the assets and technical data rights of the Corona, California operations of NavCom for approximately $27 million in cash. NavCom develops, manufactures, and supports high-reliability, mission-critical electronics, avionics and sub-assemblies. NavCom is included as a product line of Extant, which is included in TransDigm's Power and Control segment. Approximately $9.0 million of goodwill recognized for the acquisition is deductible for tax purposes over 15 years. Kirkhill – On March 15, 2018, the Company acquired the assets and certain liabilities of the Kirkhill elastomers business from Esterline Technologies for a total purchase price of approximately $49.3 million, which is net of a $0.6 million working capital settlement received in the third quarter of fiscal 2018. Kirkhill, headquartered in Brea, California, is a leading supplier of highly engineered aerospace elastomers. Kirkhill's products are used in a broad variety of most major commercial transport and military platforms. Kirkhill is included in TransDigm's Airframe segment. No goodwill recognized for the acquisition is deductible for tax purposes. Divestitures Souriau-Sunbank Companies – On December 20, 2019, TransDigm completed the divestiture Souriau-Sunbank to Eaton for approximately $920 million, which included a working capital settlement of $1.7 million. Souriau-Sunbank was acquired by TransDigm as part of its acquisition of Esterline in March 2019. The results of operations of Souriau-Sunbank are presented in discontinued operations in the accompanying consolidated financial statements for all periods presented since the date acquired. Refer to Note 23, “Discontinued Operations” for additional information. Esterline Interface Technology Group – On September 20, 2019, TransDigm completed the divestiture of its EIT group of businesses to an affiliate of KPS Capital Partners, LP for approximately $190 million, which included a working capital settlement of $0.7 million. EIT was acquired by TransDigm as part of its acquisition of Esterline in March 2019. The results of operations of EIT are presented in discontinued operations in the accompanying consolidated financial statements for all periods presented since the date acquired. Refer to Note 23, “Discontinued Operations” for additional information.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Consolidation —The accompanying consolidated financial statements were prepared in conformity with U.S. GAAP and include the accounts of TD Group and subsidiaries. All significant intercompany balances and transactions have been eliminated. Revenue Recognition —Revenue is recognized from the sale of products when control transfers to the customer, which is demonstrated by our right to payment, a transfer of title, a transfer of the risk and rewards of ownership, or the customer acceptance, but most frequently upon shipment where the customer obtains physical possession of the goods. The majority of the Company's revenue is recorded at a point in time. Sales recognized over time are generally accounted for using an input measure to determine progress completed at the end of the period. Sales for service contracts generally are recognized as the services are provided. Refer to Note 5, “Revenue Recognition,” for additional information regarding the Company’s revenue recognition policy. Shipping and Handling Costs —Shipping and handling costs are included in cost of sales in the consolidated statements of income. Research and Development Costs —The Company expenses research and development costs as incurred and classifies such amounts in selling and administrative expenses. The expense recognized for research and development costs for the fiscal years ended September 30, 2020, 2019 and 2018 was approximately $130.9 million, $116.8 million, and $73.8 million, respectively. Cash Equivalents —The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Allowance for Uncollectible Accounts —The Company reserves for amounts determined to be uncollectible based on specific identification of losses and estimated losses based on historical experience. The allowance also incorporates a provision for the estimated impact of disputes with customers. The determination of the amount of the allowance for uncollectible accounts is subject to judgment and estimation by management. If circumstances change or economic conditions deteriorate or improve, the allowance for uncollectible accounts could increase or decrease. Inventories —Inventories are stated at the lower of cost or net realizable value. Cost of inventories is generally determined by the average cost and the first-in, first-out (“FIFO”) methods and includes material, labor and overhead related to the manufacturing process. Provision for potentially obsolete or slow-moving inventory is made based on management’s analysis of inventory levels and future sales forecasts. Property, Plant and Equipment —Property, plant and equipment are stated at cost and include improvements which significantly increase capacities or extend the useful lives of existing plant and equipment. Depreciation is computed using the straight-line method over the following estimated useful lives: land improvements from 10 to 20 years, buildings and improvements from 5 to 30 years, machinery and equipment from 2 to 10 years and furniture and fixtures from 3 to 10 years. Net gains or losses related to asset dispositions are recognized in earnings in the period in which dispositions occur. Routine maintenance, repairs and replacements are expensed as incurred. Amortization expense of assets accounted for as finance leases is included within depreciation expense. Property, plant and equipment is assessed for potential impairment whenever indicators of impairment are present by determining whether the carrying value of the property can be recovered through projected, undiscounted cash flows from future operations over the property’s remaining estimated useful life. Any impairment recognized is the amount by which the carrying amount exceeds the fair value of the asset. Fair value is measured based on quoted market prices in active markets, if available. If quoted market prices are not available, the estimate of fair value is based on various valuation techniques, including the discounted value of estimated future cash flows. Debt Issuance Costs, Premiums and Discounts —The cost of obtaining financing as well as premiums and discounts are amortized using the effective interest method over the terms of the respective obligations as a component of interest expense within the consolidated statements of income. Debt issuance costs are presented in the consolidated balance sheets as a direct reduction from the carrying amount of the related debt liabilities. Financial Instruments —Interest rate swap and cap agreements are used to manage interest rate risk associated with floating-rate borrowings under our credit facility. The interest rate swap and cap agreements utilized by the Company effectively modify the Company’s exposure to interest rate risk by converting a portion of the Company’s variable rate debt to a fixed rate basis through the expiration date of the interest rate swap and cap agreements, thereby reducing the impact of interest rate volatility on future interest expense. These agreements involve the receipt of variable rate amounts in exchange for fixed rate interest payments over the term of the agreements without an exchange of the underlying principal amount. These derivative instruments qualify as effective cash flow hedges under U.S. GAAP. The Company transacts business in various foreign currencies, which subjects the Company’s cash flows and results of operations to exposure related to changes in foreign currency exchange rates. These exposures arise primarily from purchases or sales of products and services from third parties. Foreign currency forward exchange contracts provide for the purchase or sale of foreign currencies at specified future dates at specified exchange rates, and are used to offset changes in the fair value of certain assets or liabilities or forecasted cash flows resulting from transactions denominated in foreign currencies. For the interest rate swap and cap agreements and the foreign currency forward contracts designated as cash flow hedges, the effective portion of the gain or loss from the financial instruments was initially reported as a component of accumulated other comprehensive loss in stockholders’ deficit and subsequently reclassified into earnings in the same line as the hedged item in the same period or periods during which the hedged item affected earnings. As the interest rate swap and cap agreements are used to manage interest rate risk, any gains or losses from the derivative instruments that are reclassified into earnings are recognized in interest expense - net in the consolidated statements of income. As the foreign currency forward exchange contracts are used to manage foreign currency exposure primarily arising from purchases or sales from third parties, any gains or losses from the derivative instruments that are reclassified into earnings are recognized in cost of sales or net sales in the consolidated statements of income. Goodwill and Other Intangible Assets —In accordance with ASC 805, “Business Combinations,” the Company uses the acquisition method of accounting to allocate costs of acquired businesses to the assets acquired and liabilities assumed based on their estimated fair values at the dates of acquisition. The excess costs of acquired businesses over the fair values of the assets acquired and liabilities assumed were recognized as goodwill. The valuations of the acquired assets and liabilities assumed will impact the determination of future operating results. Determining the fair value of assets acquired and liabilities assumed requires management’s judgment and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash inflows and outflows, revenue growth rates, discount rates, customer attrition rates, royalty rates, asset lives and market multiples, among other items. We determine the fair values of intangible assets acquired generally in consultation with third-party valuation advisors. Fair value adjustments to the Company’s assets and liabilities are recognized and the results of operations of the acquired business are included in our consolidated financial statements from the effective date of the merger or acquisition. Intangible assets other than goodwill are recognized if the benefit of the intangible asset is obtained through contractual or other legal rights, or if the intangible asset can be sold, transferred, licensed or exchanged, regardless of the Company’s intent to do so. Goodwill is the excess of the purchase price paid over the estimated fair value of the net assets of a business acquired. Other intangible assets consist of identifiable intangibles acquired or recognized in accounting for the acquisitions (trademarks, trade names, technology, customer relationships, order backlog and other intangible assets). Goodwill and intangible assets that have indefinite useful lives (i.e., trademarks and trade names) are subject to annual impairment testing. Management determines fair value using a discounted future cash flow analysis or other accepted valuation techniques. The Company performs an annual impairment test for goodwill and other intangible assets as of the first day of the fourth fiscal quarter of each year, or more frequently, if an event occurs or circumstances change that would more likely than not reduce fair value below current value. At the time of goodwill impairment testing, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount, and whether it is therefore necessary to perform the quantitative goodwill impairment test. The quantitative goodwill impairment test consists of two steps. The first step of the goodwill impairment test, used to identify potential impairment, compares the fair value of a reporting unit (as defined) with its carrying amount, including goodwill. If the fair value of the reporting unit exceeds its carrying amount, goodwill is not considered impaired, and the second step of the goodwill impairment test is unnecessary. The second step measures the amount of impairment, if any, by comparing the carrying value of the goodwill associated with a reporting unit to the implied fair value of the goodwill derived from the estimated overall fair value of the reporting unit and the individual fair values of the other assets and liabilities of the reporting unit. U.S. GAAP requires that the annual, and any interim, impairment assessment be performed at the reporting unit level. The reporting unit level is one level below an operating segment. Substantially all goodwill was determined and recognized for each reporting unit pursuant to the accounting for the merger or acquisition as of the date of each transaction. With respect to acquisitions integrated into an existing reporting unit, any acquired goodwill is combined with the goodwill of the reporting unit. The impairment test for indefinite lived intangible assets consists of a comparison between their fair values and carrying values. If the carrying amounts of intangible assets that have indefinite useful lives exceed their fair values, an impairment loss will be recognized in an amount equal to the sum of any such excesses. The Company assesses the recoverability of its amortizable intangible assets only when indicators of impairment are present by determining whether the amortization over their remaining lives can be recovered through projected, undiscounted cash flows from future operations. Amortization of amortizable intangible assets is computed using the straight-line method over the following estimated useful lives: technology from 20 to 22 years, order backlog from 1 to 1.5 years, customer relationships over 20 years and other intangible assets over 20 years. Refer to Note 1, "Description of the Business and Impact of COVID-19 Pandemic," for further disclosures over the interim and annual impairment procedures performed during fiscal year 2020. Stock-Based Compensation —The Company records stock-based compensation expense using the Black-Scholes pricing model based on certain valuation assumptions. Compensation expense is recorded over the vesting periods of the stock options. The Company has classified stock-based compensation primarily within selling and administrative expenses to correspond with the classification of employees that receive stock option grants. No expense is recognized for any stock options ultimately forfeited because the recipients fail to meet vesting requirements. The Company also evaluates any subsequent changes to the respective option holders terms under the modification rules of ASC 718. If determined to be a modification, the Black-Scholes pricing model is updated as of the date of the modification resulting in a cumulative catch up to expense. Income Taxes —The provision for income taxes is calculated using the asset and liability method. Under the asset and liability method, deferred income taxes are recognized for the tax effect of temporary differences between the financial statement carrying amount of assets and liabilities and the amounts used for income tax purposes and for certain changes in valuation allowances. Valuation allowances are recorded to reduce certain deferred tax assets when, in our estimation, it is more likely than not that a tax benefit will not be realized. Estimates —The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Comprehensive Income (Loss) —The term “comprehensive income (loss)” represents the change in stockholders’ equity (deficit) from transactions and other events and circumstances resulting from non-stockholder sources. The Company’s accumulated other comprehensive income or loss, consisting principally of fair value adjustments to its interest rate swap and cap agreements (net of tax), cumulative foreign currency translation adjustments and pension liability adjustments (net of tax), is reported separately in the accompanying consolidated statements of comprehensive income. Foreign Currency Translation and Transactions —The assets and liabilities of subsidiaries located outside the United States are translated into U.S. dollars at the rates of exchange in effect at the balance sheet dates. Revenue and expense items are translated at the average monthly exchange rates prevailing during the period. Gains and losses resulting from foreign currency transactions are recognized currently in income, and those resulting from translation of financial statements are accumulated as a separate component of other comprehensive income (loss) for the period. Foreign currency gains or losses recognized currently in income from changes in exchange rates were immaterial to our results of operations. Earnings per Share —Earnings per share information is determined using the two-class method, which includes the weighted-average number of common shares outstanding during the period and other securities that participate in dividends (“participating securities”). Our vested stock options are considered “participating securities” because they include non-forfeitable rights to dividends. In applying the two-class method, earnings are allocated to both common stock shares and participating securities based on their respective weighted-average shares outstanding for the period. Diluted earnings per share information may include the additional effect of other securities, if dilutive, in which case the dilutive effect of such securities is calculated using the treasury stock method. Contingently issuable shares are not included in earnings per share until the period in which the contingency is satisfied; therefore, basic and diluted earnings per share are the same. Pension Benefits —The Company accounts for pension expense using the end of the fiscal year as our measurement date. Management selects appropriate assumptions including the discount rate, rate of increase in future compensation levels and assumed long-term rate of return on plan assets. The assumptions are based upon historical results, the current economic environment and reasonable expectations of future events. Actual results which vary from our assumptions are accumulated and amortized over future periods, and accordingly, are recognized in expense in these periods. Significant differences between the assumptions and actual experience or significant changes in assumptions could impact the pension costs and the pension obligation.

RECENT ACCOUNTING PRONOUNCEMENT

RECENT ACCOUNTING PRONOUNCEMENTS	12 Months Ended
	Sep. 30, 2020
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	RECENT ACCOUNTING PRONOUNCEMENTS In February 2016, the FASB issued ASU 2016-02, “Leases (ASC 842),” which requires lessees to recognize a right-of-use asset and lease liability for all leases with a term of more than 12 months. ASU 2016-02 was effective for the Company on October 1, 2019, and required a modified retrospective application. In July 2018, the FASB issued ASU 2018-11, “Leases (ASC 842) Targeted Improvements,” which provided an additional transition method that allowed entities to initially apply the new standard at the adoption date and recognize a cumulative effect adjustment to the opening balance of retained earnings in the period of adoption without restating prior periods. The Company has completed the necessary changes to the consolidated financial statements and related disclosures, internal controls, financial policies and information systems. On October 1, 2019, the Company adopted ASC 842 and related amendments using the modified retrospective method. Results for reporting periods beginning after October 1, 2019, are presented under ASC 842, while prior period amounts continue to be reported under ASC 840, “Leases." The Company elected to apply the package of practical expedients permitted within the new standard, which among other things, allow the carry forward of historical lease classification of existing leases. Additionally, the adoption of the new standard resulted in the recording of lease assets and lease liabilities for operating leases of $99 million and $105 million, respectively, as of October 1, 2019. The effects of our transition to ASC 842 resulted in no cumulative adjustment to retained earnings in the period of adoption. The adoption of the standard did not have a material impact on our results of operations or cash flows. Refer to Note 19, "Leases," for additional disclosures. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13)," which changes the impairment model for most financial assets. The new model uses a forward-looking expected loss method, which will generally result in earlier recognition of allowances for losses, and will apply to most financial assets measured at amortized cost (e.g., trade, unbilled and other receivables). ASU 2016-13 is effective for the Company on October 1, 2020 and will not materially impact the Company’s results of operations and financial condition upon adoption. In August 2018, the FASB issued ASU 2018-14, "Compensation - Retirement Benefits - Defined Benefit Plans - General (ASC 715-20)." ASC 715-20 modifies disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. ASC 715-20 also requires an entity to disclose the weighted-average interest crediting rates for cash balance plans and to explain the reasons for significant gains and losses related to changes in the benefit obligation. The Company adopted this standard in the fourth quarter of fiscal 2020. ASC 715-20 did not have a material impact on our consolidated financial statements and disclosures. In December 2019, the FASB issued ASU 2019-12, “Income Taxes (ASC 740) - Simplifying the Accounting for Income Taxes,” which simplifies the accounting for income taxes by removing certain exceptions to the general principles in ASC 740. The amendments also improve consistent application of and simplify U.S. GAAP for other areas of ASC 740 by clarifying and amending existing guidance. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption of the amendments is permitted, including adoption in any interim period for which financial statements have not yet been issued. Depending on the amendment, adoption may be applied on the retrospective, modified retrospective or prospective basis. The Company is currently evaluating the impact of adopting this standard on our consolidated financial statements and disclosures. In March 2020, the Securities and Exchange Commission adopted amendments to simplify the financial disclosure requirements for guarantors and issuers of guaranteed securities registered under Rule 3-10 of Regulation S-X. As permitted, the Company elected to early adopt these amendments during the third quarter of fiscal 2020. The amendments replace the consolidating financial information with summarized financial information of the issuers and guarantors, require expanded qualitative disclosures with respect to information about guarantors, the terms and conditions of guarantees and the factors that may affect payment, and permit these disclosures to be provided outside the notes to the parent company’s annual and interim consolidated financial statements. The Company has provided this information in Item 7. “Management’s Discussion and Analysis of Financial Condition and Results of Operations.”
New Accounting Pronouncements, Policy	RECENT ACCOUNTING PRONOUNCEMENTS In February 2016, the FASB issued ASU 2016-02, “Leases (ASC 842),” which requires lessees to recognize a right-of-use asset and lease liability for all leases with a term of more than 12 months. ASU 2016-02 was effective for the Company on October 1, 2019, and required a modified retrospective application. In July 2018, the FASB issued ASU 2018-11, “Leases (ASC 842) Targeted Improvements,” which provided an additional transition method that allowed entities to initially apply the new standard at the adoption date and recognize a cumulative effect adjustment to the opening balance of retained earnings in the period of adoption without restating prior periods. The Company has completed the necessary changes to the consolidated financial statements and related disclosures, internal controls, financial policies and information systems. On October 1, 2019, the Company adopted ASC 842 and related amendments using the modified retrospective method. Results for reporting periods beginning after October 1, 2019, are presented under ASC 842, while prior period amounts continue to be reported under ASC 840, “Leases." The Company elected to apply the package of practical expedients permitted within the new standard, which among other things, allow the carry forward of historical lease classification of existing leases. Additionally, the adoption of the new standard resulted in the recording of lease assets and lease liabilities for operating leases of $99 million and $105 million, respectively, as of October 1, 2019. The effects of our transition to ASC 842 resulted in no cumulative adjustment to retained earnings in the period of adoption. The adoption of the standard did not have a material impact on our results of operations or cash flows. Refer to Note 19, "Leases," for additional disclosures. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13)," which changes the impairment model for most financial assets. The new model uses a forward-looking expected loss method, which will generally result in earlier recognition of allowances for losses, and will apply to most financial assets measured at amortized cost (e.g., trade, unbilled and other receivables). ASU 2016-13 is effective for the Company on October 1, 2020 and will not materially impact the Company’s results of operations and financial condition upon adoption. In August 2018, the FASB issued ASU 2018-14, "Compensation - Retirement Benefits - Defined Benefit Plans - General (ASC 715-20)." ASC 715-20 modifies disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. ASC 715-20 also requires an entity to disclose the weighted-average interest crediting rates for cash balance plans and to explain the reasons for significant gains and losses related to changes in the benefit obligation. The Company adopted this standard in the fourth quarter of fiscal 2020. ASC 715-20 did not have a material impact on our consolidated financial statements and disclosures. In December 2019, the FASB issued ASU 2019-12, “Income Taxes (ASC 740) - Simplifying the Accounting for Income Taxes,” which simplifies the accounting for income taxes by removing certain exceptions to the general principles in ASC 740. The amendments also improve consistent application of and simplify U.S. GAAP for other areas of ASC 740 by clarifying and amending existing guidance. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption of the amendments is permitted, including adoption in any interim period for which financial statements have not yet been issued. Depending on the amendment, adoption may be applied on the retrospective, modified retrospective or prospective basis. The Company is currently evaluating the impact of adopting this standard on our consolidated financial statements and disclosures. In March 2020, the Securities and Exchange Commission adopted amendments to simplify the financial disclosure requirements for guarantors and issuers of guaranteed securities registered under Rule 3-10 of Regulation S-X. As permitted, the Company elected to early adopt these amendments during the third quarter of fiscal 2020. The amendments replace the consolidating financial information with summarized financial information of the issuers and guarantors, require expanded qualitative disclosures with respect to information about guarantors, the terms and conditions of guarantees and the factors that may affect payment, and permit these disclosures to be provided outside the notes to the parent company’s annual and interim consolidated financial statements. The Company has provided this information in Item 7. “Management’s Discussion and Analysis of Financial Condition and Results of Operations.”

REVENUE RECOGNITION (Notes)

REVENUE RECOGNITION (Notes)	12 Months Ended
	Sep. 30, 2020
Revenue Recognition [Abstract]
Revenue from Contract with Customer [Text Block]	REVENUE RECOGNITION TransDigm's sales are concentrated in the aerospace industry. The Company’s customers include: distributors of aerospace components, commercial airlines, large commercial transport and regional and business aircraft OEMs, various armed forces of the United States and friendly foreign governments, defense OEMs, system suppliers, and various other industrial customers. The majority of the Company's revenue is recorded at a point in time. Revenue is recognized from the sale of products when control transfers to the customer, which is demonstrated by our right to payment, a transfer of title, a transfer of the risk and rewards of ownership, or the customer acceptance, but most frequently upon shipment where the customer obtains physical possession of the goods. In some contracts, control transfers to the customer over time, primarily in contracts where the customer is required to pay for the cost of both the finished and unfinished goods at the time of cancellation plus a reasonable profit relative to the work performed for products that were customized for the customer. Therefore, we recognize revenue over time for those agreements that have a right to margin and where the products being produced have no alternative use. Based on our production cycle, it is generally expected that goods related to the revenue will be shipped and billed within the current year. For revenue recognized over time, we estimate the amount of revenue attributable to a contract earned at a given point during the production cycle based on certain costs, such as materials and labor incurred to date, plus the expected profit, which is a cost-to-cost input method. We consider the contractual consideration payable by the customer and assesses variable consideration that may affect the total transaction price. Variable consideration is included in the estimated transaction price when there is a basis to reasonably estimate the amount, including whether the estimate should be constrained in order to avoid a significant reversal of revenue in a future period. These estimates are based on historical experience, anticipated performance under the terms of the contract and our best judgment at the time. The Company’s payment terms vary by the type and location of the customer and the products or services offered. The Company does not offer any payment terms that would meet the requirements for consideration as a significant financing component. Shipping and handling fees and costs incurred in connection with products sold are recorded in cost of sales in the consolidated statements of income, and are not considered a performance obligation to our customers. The Company pays sales commissions that relate to contracts for products or services that are satisfied at a point in time or over a period of one year or less and are expensed as incurred. These costs are reported as a component of selling and administrative expenses in the consolidated statements of income. In fiscal 2020, no customer individually accounted for 10% or more of the Company’s net sales. In fiscal 2019, one customer accounted for approximately 11% of the Company’s net sales, which was split approximately 60% and 40% between the Airframe and Power & Control segments, respectively. In fiscal 2018, one customer accounted for approximately 11% of the Company’s net sales and a second customer accounted for approximately 10% of the Company’s net sales, each of which were split approximately evenly between the Power & Control and Airframe segments. Sales to foreign customers, primarily in Western Europe, Canada and Asia, were $1,696 million, $1,778 million and $1,355 million during the fiscal years ended 2020, 2019 and 2018. Contract Assets and Liabilities - Contract assets reflect revenue recognized and performance obligations satisfied in advance of customer billing or reimbursable costs related to a specific contract. Contract liabilities relate to payments received in advance of the satisfaction of performance under the contract. We receive payments from customers based on the terms established in our contracts. The following table summarizes our contract assets and liabilities balances (in millions): September 30, 2020 September 30, 2019 Change Contract assets, current (1) $ 36 $ 44 $ (8) Contract assets, non-current (2) 6 7 (1) Total contract assets 42 51 (9) Contract liabilities, current (3) 18 18 — Contract liabilities, non-current (4) 9 13 (4) Total contract liabilities 27 31 (4) Net contract assets $ 15 $ 20 $ (5) (1) Included in prepaid expenses and other on the consolidated balance sheets. (2) Included in other non-current assets on the consolidated balance sheets. (3) Included in accrued liabilities on the consolidated balance sheets. (4) Included in other non-current liabilities on the consolidated balance sheets. For the fiscal year ended September 30, 2020, the revenue recognized that was previously included in contract liabilities was not material.

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
EARNINGS PER SHARE (TWO-CLASS METHOD)	EARNINGS PER SHARE The following table sets forth the computation of basic and diluted earnings per share (in millions, except per share data) using the two-class method: Fiscal Years Ended September 30, 2020 2019 2018 Numerator for earnings per share: Income from continuing operations $ 653 $ 841 $ 962 Less: Net income attributable to noncontrolling interests (1) (2) — Net income from continuing operations attributable to TD Group 652 839 962 Less: Special dividends declared or paid on participating securities, including dividend equivalent payments (185) (111) (56) 467 728 906 Income (Loss) from discontinued operations, net of tax 47 51 (5) Net income applicable to TD Group common stockholders - basic and diluted $ 514 $ 779 $ 901 Denominator for basic and diluted earnings per share under the two-class method: Weighted-average common shares outstanding 53.9 53.1 52.3 Vested options deemed participating securities 3.4 3.2 3.3 Total shares for basic and diluted earnings per share 57.3 56.3 55.6 Earnings per share from continuing operations—basic and diluted $ 8.14 $ 12.94 $ 16.28 Earnings (Loss) per share from discontinued operations—basic and diluted 0.82 0.90 (0.08) Earnings per share $ 8.96 $ 13.84 $ 16.20

TRADE ACCOUNTS RECEIVABLE

TRADE ACCOUNTS RECEIVABLE	12 Months Ended
	Sep. 30, 2020
Receivables [Abstract]
SALES AND TRADE ACCOUNTS RECEIVABLE	TRADE ACCOUNTS RECEIVABLE Trade accounts receivable consist of the following (in millions): September 30, 2020 September 30, 2019 Trade accounts receivable—gross $ 757 $ 1,085 Allowance for uncollectible accounts (37) (17) Trade accounts receivable—net $ 720 $ 1,068

INVENTORIES

INVENTORIES	12 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
INVENTORIES	INVENTORIES Inventories consist of the following (in millions): September 30, 2020 September 30, 2019 Raw materials and purchased component parts $ 881 $ 805 Work-in-progress 358 360 Finished goods 222 192 Total 1,461 1,357 Reserves for excess and obsolete inventory (178) (124) Inventories—Net $ 1,283 $ 1,233

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	12 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment consist of the following (in millions): September 30, 2020 September 30, 2019 Land and improvements $ 103 $ 96 Buildings and improvements 350 408 Machinery, equipment and other 782 628 Construction in progress 57 52 Total 1,292 1,184 Accumulated depreciation (540) (427) Property, plant and equipment—net $ 752 $ 757

INTANGIBLE ASSETS

INTANGIBLE ASSETS	12 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS	INTANGIBLE ASSETS Other intangible assets - net in the consolidated balance sheets consist of the following at September 30 (in millions): 2020 2019 Gross Carrying Accumulated Net Gross Carrying Accumulated Net Trademarks and trade names $ 958 $ — $ 958 $ 956 $ — $ 956 Technology 1,842 589 1,253 1,806 496 1,310 Order backlog 93 93 — 107 45 62 Customer relationships 443 52 391 438 30 408 Other 18 10 8 17 9 8 Total $ 3,354 $ 744 $ 2,610 $ 3,324 $ 580 $ 2,744 Information regarding the amortization expense of amortizable intangible assets is detailed below (in millions): Annual Amortization Expense: Fiscal years ended September 30, 2020 $ 169 2019 135 2018 72 Estimated Amortization Expense: Fiscal years ending September 30, 2021 $ 115 2022 114 2023 114 2024 114 2025 114 The changes in the carrying amount of goodwill by segment for the fiscal years ended September 30, 2019 and 2020 were as follows (in millions): Power & Airframe Non- Total Balance at September 30, 2018 $ 3,678 $ 2,452 $ 93 $ 6,223 Goodwill acquired during the year (Note 2) 469 1,180 546 2,195 Divestiture of goodwill acquired — — (43) (43) Reclass of goodwill acquired to assets held-for-sale (Note 23) — — (480) (480) Purchase price allocation adjustments (1) (9) (23) — (32) Currency translation adjustments (17) (11) (15) (43) Balance at September 30, 2019 4,121 3,598 101 7,820 Purchase price allocation adjustments (1) (1) 39 — 38 Currency translation adjustments 21 10 — 31 Balance at September 30, 2020 $ 4,141 $ 3,647 $ 101 $ 7,889 (1) Primarily relates to opening balance sheet adjustments recorded by the reporting units acquired from Esterline up to the expiration of the one year measurement period in March 2020.

ACCRUED LIABILITIES

ACCRUED LIABILITIES	12 Months Ended
	Sep. 30, 2020
Payables and Accruals [Abstract]
ACCRUED LIABILITIES	ACCRUED LIABILITIES Accrued liabilities consist of the following (in millions): September 30, 2020 September 30, 2019 Compensation and related benefits $ 173 $ 178 Interest 178 93 Interest rate swap agreements 56 13 Product warranties 32 34 Dividend equivalent payments—current (Note 18) 72 64 Environmental and other litigation reserves 15 12 Income taxes payable 19 44 Loss contract reserves 42 64 Other 186 173 Total $ 773 $ 675

DEBT

DEBT	12 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
DEBT	DEBT The Company’s debt consists of the following (in millions): September 30, 2020 Gross Amount Debt Issuance Costs Original Issue Discount or Premium Net Amount Short-term borrowings—trade receivable securitization facility $ 350 $ (1) $ — $ 349 Term loans $ 7,449 $ (48) $ (23) $ 7,378 Revolving credit facility 200 — — 200 2024 Notes 1,200 (5) — 1,195 2025 Notes 750 (3) 3 750 2025 Secured Notes 1,100 (9) — 1,091 6.375% 2026 Notes 950 (6) — 944 6.875% 2026 Notes 500 (4) (3) 493 2026 Secured Notes 4,400 (55) 5 4,350 7.50% 2027 Notes 550 (5) — 545 5.50% 2027 Notes 2,650 (21) — 2,629 Government refundable advances 28 — — 28 Finance lease obligations 57 — — 57 19,834 (156) (18) 19,660 Less: current portion 277 (1) — 276 Long-term debt $ 19,557 $ (155) $ (18) $ 19,384 September 30, 2019 Gross Amount Debt Issuance Costs Original Issue Discount or Premium Net Amount Short-term borrowings—trade receivable securitization facility $ 350 $ — $ — $ 350 Term loans $ 7,524 $ (58) $ (17) $ 7,449 2022 Notes 1,150 (4) — 1,146 2024 Notes 1,200 (6) — 1,194 2025 Notes 750 (3) 3 750 6.375% 2026 Notes 950 (7) — 943 6.875% 2026 Notes 500 (6) (3) 491 2026 Secured Notes 4,000 (60) 2 3,942 7.50% 2027 Notes 550 (5) — 545 Government refundable advances 39 — — 39 Finance lease obligations 50 — — 50 16,713 (149) (15) 16,549 Less: current portion 81 (1) — 80 Long-term debt $ 16,632 $ (148) $ (15) $ 16,469 Issuance of Senior Subordinated Notes due 2027 On October 29, 2019, the Company entered into a purchase agreement in connection with a private offering of $2,650 million in new 5.50% senior subordinated notes due 2027. The 5.50% 2027 Notes were issued pursuant to an indenture, dated as of November 13, 2019, among TransDigm, as issuer, TransDigm Group, TransDigm UK and the other subsidiaries of TransDigm named therein, as guarantors. The 5.50% 2027 Notes bear interest at the rate of 5.50% per annum, which accrues from November 13, 2019 and is payable in arrears on May 15th and November 15th of each year, commencing on May 15, 2020. The 5.50% 2027 Notes mature on November 15, 2027, unless earlier redeemed or repurchased, and are subject to the terms and conditions set forth in the indenture. The Company capitalized $23.8 million and expensed $1.1 million of refinancing costs representing debt issue costs associated with the 5.50% 2027 Notes during the fiscal year ended September 30, 2020 . Repurchase of Senior Subordinated Notes due 2022 On October 29, 2019, the Company announced a cash tender offer for any and all of its 2022 Notes outstanding. On November 26, 2019, the Company redeemed the principal amount of $1,150 million, plus accrued interest of approximately $25.5 million and early redemption premium of $17.3 million. The Company wrote off $3.8 million in unamortized debt issue costs during the fiscal year ended September 30, 2020 in conjunction with the redemption of the 2022 Notes. Amendment No. 7 and Refinancing Facility Agreement On February 6, 2020, the Company entered into Amendment No. 7 to the Second Amended and Restated Credit Agreement dated as of June 4, 2014 (the “Credit Agreement”). Under the terms of Amendment No. 7, the Company, among other things, (i) incurred new tranche E term loans in an aggregate principal amount equal to approximately $2,216 million, new tranche F term loans in an aggregate principal amount equal to approximately $3,515 million and new tranche G term loans, in an aggregate principal amount equal to approximately $1,774 million, (ii) repaid in full all of the prior existing tranche E term loans, tranche F term loans and tranche G term loans outstanding under the Credit Agreement immediately prior to Amendment No. 7 and (iii) extend the maturity date of the new tranche F term loans to December 9, 2025. The New Term Loans were fully drawn on February 6, 2020. The LIBOR per annum applicable to the New Term Loans is 2.25%, a decrease from the 2.50% rate that previously applied. In addition to a discount of $8.8 million recorded in conjunction with the new tranche F term loans, the Company capitalized $3.4 million and expensed $4.5 million of refinancing costs representing debt issue costs associated with Amendment No. 7 during the fiscal year ended September 30, 2020 . Revolving Credit Facility On March 24, 2020, the Company drew $200 million on its revolving credit facility to increase the Company's liquidity as a precautionary response to macroeconomic conditions caused by the COVID-19 pandemic. The revolving credit facility bears interest at a rate of 3.00% plus 0.75% or LIBOR, whichever is greater. At September 30, 2020, the applicable interest rate was 3.75%. As of September 30, 2020, the Company had $39.4 million in letters of credit outstanding and $520.6 million of borrowings available under the revolving credit facility. Issuance of Senior Secured Notes due 2025 On April 8, 2020, the Company entered into a purchase agreement in connection with a private offering of $1,100 million in aggregate principal amount of 8.00% Senior Secured Notes due 2025 at an issue price of 100% of the principal amount. The 2025 Secured Notes were issued pursuant to an indenture, dated as of April 8, 2020, amongst TransDigm, as issuer, TransDigm Group, TransDigm UK and the other subsidiaries of TransDigm named therein, as guarantors. The 2025 Secured Notes are secured by a first-priority security interest in substantially all the assets of TransDigm, TransDigm Group, TransDigm UK and each other guarantor on an equal and ratable basis with any other existing and future senior secured debt, including indebtedness under the Company's senior secured credit facilities and the 2026 Secured Notes. The 2025 Secured Notes bear interest at the rate of 8.00% per annum, which accrues from April 8, 2020 and is payable in arrears on April 1 and October 1 of each year, commencing on October 1, 2020. The 2025 Secured Notes mature on December 15, 2025, unless earlier redeemed or repurchased, and are subject to the terms and conditions set forth in the indenture. The Company capitalized $10.1 million of refinancing costs representing debt issue costs associated with the 2025 Secured Notes during the fiscal year ended September 30, 2020. Issuance of Senior Secured Notes due 2026 On April 17, 2020, the Company entered into a purchase agreement in connection with a private offering of $400 million in aggregate principal amount of 6.25% Senior Secured Notes due 2026 at an issue price of 101% of the principal amount. The 6.25% 2026 New Notes are an additional issuance of the Company's existing 2026 Secured Notes, and were issued under the indenture dated as of February 13, 2019 pursuant to which the Company previously issued $4,000 million. The 6.25% 2026 New Notes are the same class and series as, and otherwise identical to, the 2026 Secured Notes other than with respect to the date of issuance and issue price. The 6.25% 2026 New Notes bear interest at a rate of 6.25% per annum, which accrues from March 15, 2020 and is payable semiannually in arrears on March 15th and September 15th of each year, commencing on September 15, 2020. The 6.25% 2026 New Notes mature on March 15, 2026, unless earlier redeemed or repurchased, and are subject to the terms and conditions set forth in the indenture. The Company capitalized $5.4 million of refinancing costs representing debt issue costs associated with the 6.25% 2026 New Notes during the fiscal year ended September 30, 2020. Trade Receivable Securitization Facility During fiscal 2014, the Company established a trade receivable securitization facility (the “Securitization Facility”). The Securitization Facility effectively increases the Company’s borrowing capacity depending on the amount of the domestic operations’ trade accounts receivable. The Securitization Facility includes the right for the Company to exercise annual one year extensions as long as there have been no termination events as defined by the agreement. The Company uses the proceeds from the Securitization Facility as an alternative to other forms of debt, effectively reducing borrowing costs. On July 22, 2020, the Company amended the Securitization Facility to extend the maturity date to July 27, 2021. As of September 30, 2020, the Company has borrowed $350 million under the Securitization Facility, which bears interest at a rate of 1.35% plus 0.50% or LIBOR, whichever is greater. At September 30, 2020, the applicable interest rate was 1.85%. The Securitization Facility is collateralized by substantially all of the Company’s domestic operations’ trade accounts receivable. Government Refundable Advances Government refundable advances consist of payments received from the Canadian government to assist in research and development related to commercial aviation. The requirement to repay this advance is solely based on year-over-year commercial aviation revenue growth at CMC Electronics, which is a subsidiary of TransDigm. As of September 30, 2020 and 2019, the outstanding balance of these advances were $28.4 million and $39.2 million, respectively. Obligations under Finance Leases The Company leases certain buildings and equipment under finance leases. The present value of the minimum finance lease payments, net of the current portion, represents a balance of $56.8 million and $49.9 million at September 30, 2020 and 2019, respectively. Refer to Note 19, “Leases,” for further disclosure of the Company’s lease obligations. Term Loans As of September 30, 2020 and 2019, TransDigm had $7,449 million and $7,524 million in fully drawn term loans and $760 million in revolving commitments, of which $521 million and $719 million was available to the Company as of September 30, 2020 and 2019, respectively. The term loans consist of three tranches as follows (in millions): Term Loan Facility Maturity Date Interest Rate Aggregate Principal as of September 30, 2020 2019 Tranche E May 30, 2025 LIBOR + 2.25% $ 2,199 $ 2,221 Tranche F December 9, 2025 LIBOR + 2.25% $ 3,489 $ 3,524 Tranche G August 22, 2024 LIBOR + 2.25% $ 1,761 $ 1,779 The interest rates per annum applicable to all of the existing tranches of term loans are, at TransDigm’s option, equal to either an alternate base rate or an adjusted LIBOR for one, two, three or six-month (or to the extent agreed to by each relevant lender, nine or twelve-month) interest periods chosen by TransDigm, in each case plus an applicable margin percentage. The adjusted LIBOR is not subject to a floor. At September 30, 2020 and 2019, the applicable interest rates for all existing tranches were 2.41% and 4.83%, respectively. Refinancing Costs During the fiscal year ended September 30, 2020, the Company recorded refinancing costs of $28 million primarily representing the early redemption premium paid in connection with the repurchase of the $1,150 million 6.00% 2022 Notes, and also the execution of Amendment No. 7 and the Refinancing Facility Agreement. During the fiscal year ended September 30, 2019, the Company recorded refinancing costs of $3 million representing the early redemption premium paid in connection with the repurchase of the $550 million 2020 Senior Subordinated Notes and issuance of the $4.0 billion 2026 Senior Secured Notes. During the fiscal year ended September 30, 2018, the Company recorded refinancing costs of $6 million representing the refinancing of term loans, and issuance of the $500 million 6.875% Senior Subordinated Notes. Interest Rate Swap and Cap Agreements See Note 21, “Derivatives and Hedging Activities,” for information about how our interest rate swap and cap agreements are used to manage interest rate risk associated with floating-rate borrowings under our credit facilities. Secured Notes TransDigm Inc.’s 2025 Secured Notes and 2026 Secured Notes jointly and severally guaranteed, on a senior basis, by TD Group, TransDigm UK and all of TransDigm Inc.'s Domestic Restricted Subsidiaries, as defined in the applicable Indentures. The Secured Notes contain many of the restrictive covenants included in the Credit Agreement. TransDigm is in compliance with all the covenants contained in the notes. Subordinated Notes TransDigm Inc.'s 2024 Notes, 2025 Notes, 6.375% 2026 Notes, 7.50% 2027 Notes and 5.50% 2027 Notes are jointly and severally guaranteed, on a senior subordinated basis, by TD Group, TransDigm UK and all of TransDigm Inc.'s Domestic Restricted Subsidiaries, as defined in the applicable Indenture. TransDigm UK's 6.875% 2026 Notes are jointly and severally guaranteed, on a senior subordinated basis, by TD Group, TransDigm Inc. and all of TransDigm Inc.'s Domestic Restricted Subsidiaries, as defined in the applicable Indenture. The Notes contain many of the restrictive covenants included in the Credit Agreement. TransDigm is in compliance with all the covenants contained in the notes. Debt Repayment Schedule At September 30, 2020, future maturities of long-term debt (includes finance leases) are as follows (in millions): Fiscal years ending September 30, 2021 $ 77 2022 81 2023 281 2024 2,970 2025 2,902 Thereafter 13,523 $ 19,834

RETIREMENT PLANS

RETIREMENT PLANS	12 Months Ended
	Sep. 30, 2020
Retirement Benefits [Abstract]
RETIREMENT PLANS	RETIREMENT PLANS The Company maintains certain non-contributory defined benefit pension plans. The plans provide benefits of stated amounts for each year of service. The Company’s funding policy is to contribute actuarially determined amounts allowable under tax and statutory regulations for the qualified plans. The Company uses a September 30th measurement date for its defined benefit pension plans. In addition, the Company makes actuarially computed contributions to these plans as necessary to adequately fund benefits. The Company’s funding policy is consistent with the minimum funding requirements of the Employee Retirement Income Security Act of 1974 (“ERISA”). The Company sponsors a number of U.S. defined benefit pension plans, with the largest plan being the Esterline Retirement Plan (“ERP”). Under the ERP, pension benefits are primarily earned under a cash balance formula with annual pay credits ranging from 2% to 6%. The weighted average interest crediting rate for the plan is 5.50% for fiscal years 2020 and 2019. The Company also sponsors other retirement benefit plans for certain employees in the U.S., such as non-contributory health care and life insurance plans. The Company sponsors a number of non-U.S. defined benefit pension plans primarily in Canada, Belgium, France, Germany and the United Kingdom. These defined benefit plans generally provide benefits to employees based on formulas recognizing length of service and earnings. The Company also sponsors other retirement benefit plans for its employees in Canada. Other retirement benefit plans are non-contributory health care and life insurance plans. The accumulated benefit obligation and projected benefit obligation for the U.S. plans are $358.1 million and $366.2 million, respectively, with plan assets of $342.0 million as of September 30, 2020. The underfunded status for the Company’s U.S. plans is $24.2 million at September 30, 2020, all of which is for the Company’s qualified U.S. plans. As of September 30, 2020, a $19.4 million decrease to the projected benefit obligation is due to settlements that occurred in fiscal 2020. Contributions to the Company’s qualified and non-qualified U.S. plans totaled $1.7 million and $19.8 million, respectively, in fiscal 2020. Contributions to the Company’s qualified and non-qualified U.S. plans totaled $1.4 million and $0.9 million, respectively, in fiscal 2019. There is an expected funding requirement of $0.9 million for fiscal 2021 for the qualified U.S. pension plans maintained by the Company. The accumulated benefit obligation and projected benefit obligation for the non-U.S. plans are $237.2 million and $247.8 million, respectively, with plan assets of $204.3 million as of September 30, 2020. The underfunded status for these non-U.S. plans is $47.5 million at September 30, 2020. As of September 30, 2020, a $40.1 million decrease to the projected benefit obligation is due to settlements that occurred in fiscal 2020. Contributions to the non-U.S. plans totaled $8.3 million and $2.7 million in fiscal 2020 and 2019, respectively. The expected funding requirement for fiscal 2021 for the non-U.S. plans is $3.1 million. U.S. Defined Benefit Pension Plans Non-U.S. Defined Benefit Pension Plans Principal assumptions as of year end: 2020 2019 2020 2019 Discount rate 2.47% 3.03% 1.90% 2.20% Rate of increase in future compensation levels 4.45% 4.48% 2.90% 2.98% Assumed long-term rate of return on plan assets 5.99% 6.00% 3.69% 4.16% U.S. Post-Retirement Pension Plans Non-U.S. Post Retirement Pension Plans Principal assumptions as of year end: 2020 2019 2020 2019 Discount rate 1.99% 2.86% 2.28% 2.68% Initial weighted average health care trend rate 7.27% 7.46% 5.50% 5.60% Ultimate weighted average health care trend rate 6.00% 6.00% 4.10% 4.10% The Company uses discount rates developed from a yield curve established from high-quality corporate bonds and matched to plan-specific projected benefit payments. Although future changes to the discount rate are unknown, had the discount rate increased or decreased by 25 basis points, pension liabilities in total would have decreased $20.3 million or increased $17.1 million, respectively. Had the discount rate increased or decreased by 25 basis points, fiscal 2020 net periodic benefit cost for the pension plans would have increased $0.2 million or decreased $0.1 million, respectively. In determining the expected long-term rate of return on the defined benefit pension plans’ assets, the Company considers the historical rates of return, the nature of investments, the asset allocation, and expectations of future investment strategies. Had the expected return on assets increased or decreased by 25 basis points, fiscal 2020 net periodic benefit cost would have decreased $1.3 million or increased $1.3 million, respectively. Management is not aware of any legislative or other initiatives or circumstances that will significantly impact the Company’s pension obligations in fiscal 2021. Plan assets are invested in a diversified portfolio of equity and debt securities consisting primarily of common stocks, bonds and government securities. The objective of these investments is to maintain sufficient liquidity to fund current benefit payments and achieve targeted risk-adjusted returns. Management periodically reviews allocations of plan assets by investment type and evaluates external sources of information regarding the long-term historical returns and expected future returns for each investment type. Allocations by investment type are as follows : Actual Plan assets allocation as of fiscal year end: Target 2020 2019 Equity securities 35 - 70% 39.1% 35.1% Debt securities 30 - 65% 57.0% 59.5% Cash —% 3.9% 5.4% Total 100.0% 100.0% The following table presents the fair value of the Company’s pension plan assets as of September 30, 2020, by asset category segregated by level within the fair value hierarchy, as described in Note 20, “Fair Value Measurements” (in millions): Fair Value Hierarchy Level 1 Level 2 Total Investments measured at fair value by category: Equity Funds: (1) U.S. Equity Securities $ 4 $ — $ 4 Non-U.S. Equity Securities 48 — 48 Fixed Income Securities: (2) Non-U.S. Foreign Commercial and Government Bonds — 58 58 Cash and Cash Equivalents (3) 22 — 22 $ 74 $ 58 $ 132 Investments measured at net asset value by category: (4) Equity Funds: (1) Commingled Trust Funds - Non-U.S. Securities 153 Non-U.S. Equity Securities 9 Fixed Income Securities: (2) U.S. Government Bonds and Securities 80 U.S Corporate Bonds 123 Non-U.S. Corporate Bonds 18 Non-U.S. Foreign Commercial and Government Bonds 31 Total $ 546 The following table presents the fair value of the Company’s pension plan assets as of September 30, 2019, by asset category segregated by level within the fair value hierarchy, as described in Note 20, “Fair Value Measurements” (in millions): Fair Value Hierarchy Level 1 Level 2 Total Investments measured at fair value by category: Equity Funds: (1) U.S. Equity Securities $ 3 $ — $ 3 Non-U.S. Equity Securities 48 — 48 Fixed Income Securities: (2) Non-U.S. Foreign Commercial and Government Bonds — 86 86 Cash and Cash Equivalents (3) 30 — 30 $ 81 $ 86 $ 167 Investments measured at net asset value by category: (4) Equity Funds: (1) Commingled Trust Funds - Non-U.S. Securities 142 Fixed Income Securities: (2) U.S. Government Bonds and Securities 86 U.S Corporate Bonds 108 Non-U.S. Corporate Bonds 18 Non-U.S. Foreign Commercial and Government Bonds 30 Total $ 551 (1) Level 1 Equity Securities are actively traded on U.S. and non-U.S. exchanges and are either valued using the market approach at quoted market prices on the measurement date or at the net asset value of the shares held by the plan on the measurement date based on quoted market prices. (2) Level 2 Fixed Income Securities are primarily valued using the market approach at either quoted market prices, pricing models that use observable market data, or bids provided by independent investment brokerage firms. (3) Cash and Cash Equivalents include cash which is used to pay benefits and cash invested in a short-term investment fund that holds securities with values based on quoted market prices, but for which the funds are not valued on quoted market basis. (4) These investments are valued at the net asset value (“NAV”) of units held. The NAV is used to estimate fair value and is based on the fair value of the underlying investments held by the fund less its liability. Net periodic pension cost for the Company’s U.S. and non-U.S. defined benefit pension plans at the end of each fiscal year consisted of the following (in millions): Defined Benefit Pension Plans 2020 2019 2018 U.S. Pension Plans Non-U.S. Pension Plans U.S. Pension Plans Non-U.S. Pension Plans U.S. Pension Plans Non-U.S. Pension Plans Service cost $ 9 $ 6 $ 5 $ 3 $ 1 $ 1 Interest cost 10 5 7 5 1 2 Expected return on plan assets (19) (8) (10) (6) (1) (3) Amortization of actuarial loss (gain) 1 1 — — — 1 Curtailment/settlement loss (gain) (1) (1) — — — — Net periodic pension cost $ — $ 3 $ 2 $ 2 $ 1 $ 1 Net periodic pension cost for the Company’s U.S. and non-U.S. post-retirement pension plans was less than $1 million at the end of fiscal year 2020, 2019 and 2018. The components of net periodic pension costs other than service cost are included in other (income) expense in the consolidated statements of income. The funded status of the defined benefit pension and post-retirement plans at the end of fiscal 2020 and 2019 were as follows (in millions): Defined Benefit Pension Plans Post-Retirement Pension Plans September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 U.S. Pension Plans Non-U.S. Pension Plans U.S. Pension Plans Non-U.S. Pension Plans U.S. Pension Plans Non-U.S. Pension Plans U.S. Pension Plans Non-U.S. Pension Plans Benefit Obligations Beginning balance $ 379 $ 270 $ 19 $ 73 $ 1 $ 14 $ 1 $ — Currency translation adjustment — 5 — (4) — — — — Service cost 9 6 5 3 — — — — Interest cost 10 5 8 5 — — — — Plan participant contributions — 1 — — — — — — Actuarial loss 10 13 43 28 — 1 — 1 Acquisitions — — 318 171 — — — 13 Curtailments — (2) — — — — — — Settlements (20) (40) — — — — — — Other adjustments — — — 1 — — — — Benefits paid (22) (10) (14) (7) — (1) — — Ending balance $ 366 $ 248 $ 379 $ 270 $ 1 $ 14 $ 1 $ 14 Plan Assets - Fair Value Beginning balance $ 318 $ 234 $ 9 $ 60 $ — $ — $ — $ — Currency translation adjustment — 3 — (3) — — — — Realized and unrealized gain on plan assets 44 8 31 19 — — — — Plan participants contributions — 1 — — — — — — Company contributions 21 8 2 3 — 1 — — Settlements (19) (40) — — — — — — Acquisitions — — 290 162 — — — — Other adjustments — — — — — — — — Expenses paid — — — — — — — — Benefits paid (22) (10) (14) (7) — (1) — — Ending balance $ 342 $ 204 $ 318 $ 234 $ — $ — $ — $ — Funded Status Fair value of plan assets $ 342 $ 204 $ 318 $ 234 $ — $ — $ — $ — Benefit obligations (366) (248) (379) (270) (1) (14) (1) (14) Net amount recognized $ (24) $ (44) $ (61) $ (36) $ (1) $ (14) $ (1) $ (14) Amount Recognized on Consolidated Balance Sheet Non-current asset $ — $ 4 $ — $ 4 $ — $ — $ — $ — Current liability (1) (1) (2) — — (1) — (1) Non-current liability (23) (47) (59) (40) (1) (13) (1) (13) Net amount recognized $ (24) $ (44) $ (61) $ (36) $ (1) $ (14) $ (1) $ (14) Amounts Recognized in Accumulated Other Comprehensive Income Net actuarial loss $ 12 $ 35 $ 28 $ 23 $ — $ 2 $ — $ 1 Prior service cost 1 1 1 1 — — — — Ending balance $ 13 $ 36 $ 29 $ 24 $ — $ 2 $ — $ 1 The accumulated benefit obligation for all pension plans was $595.3 million at September 30, 2020 and $623.8 million at September 30, 2019. Estimated future benefit payments expected to be paid from the pension and post-retirement benefit plans or from the Company’s assets are as follows (in millions): Fiscal Year 2021 $ 31 2022 31 2023 32 2024 33 2025 34 2026 - 2030 182 Defined Contribution Plans The Company sponsors certain defined contribution employee savings plans that cover substantially all of the Company’s U.S. employees. Under certain plans, the Company contributes a percentage of employee compensation and matches a portion of employee contributions. The cost recognized for such contributions for the fiscal years ended September 30, 2020, 2019 and 2018 was approximately $25.3 million, $24.5 million and $14.9 million, respectively.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company’s income from continuing operations before income taxes includes the following components for the periods shown below (in millions): Fiscal Years Ended September 30, 2020 2019 2018 United States $ 635 $ 878 $ 827 Foreign 105 185 159 $ 740 $ 1,063 $ 986 The Company’s income tax provision on income from continuing operations consists of the following for the periods shown below (in millions): Fiscal Years Ended September 30, 2020 2019 2018 Current Federal $ 26 $ 154 $ 137 State 3 15 12 Foreign 34 54 27 63 223 176 Deferred 24 (1) (152) $ 87 $ 222 $ 24 The differences between the income tax provision on income from continuing operations at the federal statutory income tax rate and the tax provision shown in the accompanying consolidated statements of income for the periods shown below are as follows (in millions): Fiscal Years Ended September 30, 2020 2019 2018 Tax at statutory rate of 21% (21% for fiscal 2019 and 24.5% for fiscal 2018 ) $ 155 $ 223 $ 242 Stock compensation (79) (58) (51) Domestic manufacturing deduction — — (15) U.S. tax reform (1) — — (146) Foreign rate differential 5 2 (14) Foreign derived intangible income (20) (16) — Foreign tax credits (5) (18) (3) Changes in valuation allowances impacting results (2) 31 66 — Other—net — 23 11 Income tax provision $ 87 $ 222 $ 24 (1) On December 22, 2017, the Tax Cuts and Jobs Act (the “Act”) was enacted. The Act reduces the U.S. federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings from certain foreign subsidiaries that were previously deferred as well as other changes. We recorded tax benefits of $176.4 million related to the remeasurement of our net U.S. deferred tax liabilities to reflect the reduction in the corporate tax rate. We also recorded tax expense of $30.0 million related to the one-time transition tax. (2) Primarily relates to the Company’s business interest expense limitation pursuant to IRC §163(j) as modified by the Act. Such provision, as modified, is effective for the Company beginning in fiscal 2019. In general, the deduction for interest expense is limited to 30% (50% as modified by the CARES Act for the Company’s fiscal 2020 and 2021) of the sum of the Company’s adjusted taxable income (“ATI”) and its business interest income. Interest expense disallowed by such limitation, in a taxable year, may be carried forward indefinitely. Based upon available evidence, a valuation allowance was recorded for the resulting carryforward to reflect the Company’s belief that it is more likely than not that such deferred tax assets will not be realized. The components of the deferred taxes consist of the following at September 30 (in millions): 2020 2019 Deferred tax assets (liabilities): Intangible assets $ (730) $ (710) Property, plant and equipment (59) (64) Employee benefits 110 123 Interest rate swaps and caps 92 55 U.S. interest expense limitation 87 65 Loss contract reserves 55 63 Net operating losses 54 58 Inventories 41 39 Non-U.S. income tax credits 21 24 U.S. income tax credits 17 17 Environmental reserves 12 10 Product warranty reserves 10 8 Other 9 4 Total (281) (308) Add: Valuation allowance (132) (118) Total net deferred tax $ (413) $ (426) At September 30, 2020, the Company has state net operating loss carryforwards of approximately $1,482.1 million, Belgium net operating loss carryforwards of $47.0 million, German net operating loss carryforwards of $18.1 million and United Kingdom net operating loss carryforwards of approximately $12.3 million that expire in various years from 2020 to 2039. The Company had U.S. and non-U.S. tax credit carryforwards of $38.2 million that expire beginning in 2025. The deferred tax assets for the interest expense limitation, net operating losses, and tax credit carryforwards are reduced by a valuation allowance for the amount of such assets that the Company believes will not be realized. The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction and various state, local and foreign jurisdictions. The Company is no longer subject to U.S. federal examinations for years before fiscal 2015.The Company is currently under examination for its federal income taxes in the U.S. for fiscal 2016, in Belgium for fiscal years 2016 through 2018, in Canada for fiscal years 2013 through 2015, and in France for fiscal years 2015 through 2018. The Company expects the examination in France to be completed during fiscal 2021. In addition, the Company is subject to state income tax examinations for fiscal years 2015 and later. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in millions): 2020 2019 Balance at October 1 $ 37 $ 14 Additions based on tax positions related to the prior year 7 26 Additions based on tax positions related to the current year 2 — Reductions based on tax positions related to the prior year (1) (2) Settlement with tax authorities (2) — Lapse in statute of limitations (2) (1) Balance at September 30 $ 41 $ 37 Unrecognized tax benefits at September 30, 2020 and 2019, the recognition of which would have an effect on the effective tax rate for each fiscal year, amounted to $40.9 million and $36.7 million, respectively. The Company classifies all income tax related interest and penalties as income tax expense, which were not significant for the years ended September 30, 2020 and 2019. As of September 30, 2020 and 2019, the Company accrued $8.7 million and $5.0 million, respectively, for the potential payment of interest and penalties. Within the next 12 months, it is reasonably possible that unrecognized tax benefits could be reduced by approximately $20.0 million resulting from resolution or closure of tax examinations. Any increase in the amount of unrecognized tax benefits within the next 12 months is expected to be insignificant.

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Notes)	12 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure [Text Block]	COMMITMENTS AND CONTINGENCIES During the ordinary course of business, the Company is from time to time threatened with, or may become a party to, legal actions and other proceedings. While the Company is currently involved in certain legal proceedings, it believes the results of these proceedings will not have a material adverse effect on its financial condition, results of operations, or cash flows. Environmental Liabilities Our operations and facilities are subject to a number of federal, state, local and foreign environmental laws and regulations that govern, among other things, discharges of pollutants into the air and water, the generation, handling, storage and disposal of hazardous materials and wastes, the remediation of contamination and the health and safety of our employees. Environmental laws and regulations may require that the Company investigate and remediate the effects of the release or disposal of materials at sites associated with past and present operations. Certain facilities and third-party sites utilized by the Company have been identified as potentially responsible parties under the federal superfund laws and comparable state laws. The Company is currently involved in the investigation and remediation of a number of sites under applicable laws. Estimates of the Company’s environmental liabilities are based on current facts, laws, regulations and technology. These estimates take into consideration the Company’s prior experience and professional judgment of the Company’s environmental advisors. Estimates of the Company’s environmental liabilities are further subject to uncertainties regarding the nature and extent of site contamination, the range of remediation alternatives available, evolving remediation standards, imprecise engineering evaluations and cost estimates, the extent of corrective actions that may be required and the number and financial condition of other potentially responsible parties, as well as the extent of their responsibility for the remediation. Accordingly, as investigation and remediation proceed, it is likely that adjustments in the Company’s accruals will be necessary to reflect new information. The amounts of any such adjustments could have a material adverse effect on the Company’s results of operations or cash flows in a given period. Based on currently available information, however, the Company does not believe that future environmental costs in excess of those accrued with respect to sites for which the Company has been identified as a potentially responsible party are likely to have a material adverse effect on the Company’s financial condition. Environmental liabilities are recorded when the liability is probable and the costs are reasonably estimable, which generally is not later than at completion of a feasibility study or when the Company has recommended a remedy or has committed to an appropriate plan of action. The Company also takes into consideration the estimated period of time in which payments will be required. The liabilities are reviewed periodically and, as investigation and remediation proceed, adjustments are made as necessary. Liabilities for losses from environmental remediation obligations do not consider the effects of inflation and anticipated expenditures are not discounted to their present value. The liabilities are not offset by possible recoveries from insurance carriers or other third parties, but do reflect anticipated allocations among potentially responsible parties at federal superfund sites or similar state-managed sites, third party indemnity obligations, and an assessment of the likelihood that such parties will fulfill their obligations at such sites. The Company’s consolidated balance sheets includes current environmental remediation obligations at September 30, 2020 and 2019 of $7.9 million and $9.4 million classified as a component of accrued liabilities, respectively, and non-current environmental remediation obligations at September 30, 2020 and 2019 of $43.1 million and $32.7 million classified as a component of other non-current liabilities, respectively. Leach International Europe - Fire On August 8, 2019, a fire caused significant damage to the Niort, France operating facility of Leach International Europe, a subsidiary of TransDigm. Leach International Europe’s results are reported within the Company’s Power & Control segment. The facility as well as certain machinery, equipment and inventory sustained damage. The Company suspended operations at the Niort facility as a result of the fire and transferred certain operations to temporary facilities until operations are fully restored at the rebuilt facility in Niort. The new facility is estimated to be complete and fully operational during the second quarter of fiscal 2021.

CAPITAL STOCK

CAPITAL STOCK	12 Months Ended
	Sep. 30, 2020
Equity [Abstract]
CAPITAL STOCK	CAPITAL STOCKTD Group consists of 224,400,000 shares of $.01 par value common stock and 149,600,000 shares of $.01 par value preferred stock. The total number of shares of common stock issued at September 30, 2020 and 2019 was 58,612,028 and 57,623,311, respectively. The total number of shares held in treasury at September 30, 2020 and 2019 was 4,198,226 and 4,161,326, respectively. There were no shares of preferred stock outstanding at September 30, 2020 and 2019. The terms of the preferred stock have not been established.On November 8, 2017, our Board of Directors, authorized a stock repurchase program permitting repurchases of our outstanding shares not to exceed $650 million in the aggregate, subject to any restrictions specified in the Credit Agreement and/or Indentures governing the existing Notes. During March 2020, the Company repurchased 36,900 shares of its common stock at a gross cost of $18.9 million at the weighted average cost of $512.67 under the $650 million stock repurchase program. No repurchases were made under the program during the fiscal year ended September 30, 2019. As of September 30, 2020, the remaining amount of repurchases allowable under the $650 million program was $631.1 million subject to any restrictions specified in the Credit Agreement and/or Indentures governing the existing Notes.

SEGMENTS

SEGMENTS	12 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
SEGMENTS	SEGMENTS The Company’s businesses are organized and managed in three reporting segments: Power & Control, Airframe and Non-aviation. The Power & Control segment includes operations that primarily develop, produce and market systems and components that predominately provide power to or control power of the aircraft utilizing electronic, fluid, power and mechanical motion control technologies. Major product offerings include mechanical/electro-mechanical actuators and controls, ignition systems and engine technology, specialized pumps and valves, power conditioning devices, specialized AC/DC electric motors and generators, batteries and chargers, databus and power controls, advanced sensor products, switches and relay panels, high performance hoists, winches and lifting devices, and cargo loading, handling and delivery systems. Primary customers of this segment are engine and power system and subsystem suppliers, airlines, third party maintenance suppliers, military buying agencies and repair depots. Products are sold in the original equipment and aftermarket market channels. The Airframe segment includes operations that primarily develop, produce and market systems and components that are used in non-power airframe applications utilizing airframe and cabin structure technologies. Major product offerings include engineered latching and locking devices, engineered rods, engineered connectors and elastomer sealing solutions, cockpit security components and systems, specialized and advanced cockpit displays, aircraft audio systems, specialized lavatory components, seat belts and safety restraints, engineered and customized interior surfaces and related components, thermal protection and insulation, lighting and control technology and parachutes. Primary customers of this segment are airframe manufacturers and cabin system suppliers and subsystem suppliers, airlines, third party maintenance suppliers, military buying agencies and repair depots. Products are sold in the original equipment and aftermarket market channels. The Non-aviation segment includes operations that primarily develop, produce and market products for non-aviation markets. Major product offerings include headsets for high-noise, medium-noise, and dismounted applications, seat belts and safety restraints for ground transportation applications, mechanical/electro-mechanical actuators and controls for space applications, hydraulic/electromechanical actuators and fuel valves for land based gas turbines, and refueling systems for heavy equipment used in mining, construction and other industries and turbine controls for the energy and oil and gas markets. Primary customers of this segment are off-road vehicle suppliers and subsystem suppliers, child restraint system suppliers, satellite and space system suppliers, manufacturers of heavy equipment used in mining, construction and other industries and turbine original equipment manufacturers, gas pipeline builders and electric utilities. The Esterline businesses were acquired during the second quarter of fiscal 2019 and preliminarily assessed as a separate segment of the Company. During the third quarter of fiscal 2019, the Esterline businesses were integrated into TransDigm's existing Power & Control, Airframe, and Non-Aviation segments. Previously reported operating results for the Esterline businesses were reclassified to conform to the presentation for the fiscal year ended September 30, 2020. The re-segmentation did not impact prior period results. The primary measurement used by management to review and assess the operating performance of each segment is EBITDA As Defined. The Company defines EBITDA As Defined as earnings before interest, taxes, depreciation and amortization plus certain non-operating items recorded as corporate expenses including refinancing costs, acquisition-related costs, transaction-related costs, foreign currency gains and losses, and non-cash compensation charges incurred in connection with the Company’s stock incentive plans. Acquisition-related costs represent accounting adjustments to inventory associated with acquisitions of businesses and product lines that were charged to cost of sales when the inventory was sold; costs incurred to integrate acquired businesses and product lines into the Company’s operations, facility relocation costs and other acquisition-related costs; transaction related costs comprising deal fees; legal, financial and tax diligence expenses and valuation costs that are required to be expensed as incurred and other acquisition accounting adjustments. EBITDA As Defined is not a measurement of financial performance under U.S. GAAP. Although the Company uses EBITDA As Defined to assess the performance of its business and for various other purposes, the use of this non-GAAP financial measure as an analytical tool has limitations, and it should not be considered in isolation or as a substitute for analysis of the Company’s results of operations as reported in accordance with U.S. GAAP. The Company’s segments are reported on the same basis used internally for evaluating performance and for allocating resources. The accounting policies for each segment are the same as those described in the summary of significant accounting policies in the Company’s consolidated financial statements. Intersegment sales and transfers are recorded at values based on market prices, which creates intercompany profit on intersegment sales or transfers that is eliminated in consolidation. Intersegment sales were immaterial for the periods presented below. Certain corporate-level expenses are allocated to the operating segments. The following table presents net sales by reportable segment (in millions): Fiscal Years Ended September 30, 2020 2019 2018 Net sales to external customers Power & Control Commercial OEM $ 623 $ 686 $ 499 Commercial Aftermarket 673 769 665 Defense 1,399 1,281 975 Total Power & Control 2,695 2,736 2,139 Airframe Commercial OEM 783 836 509 Commercial Aftermarket 689 865 701 Defense 781 628 321 Total Airframe 2,253 2,329 1,531 Total Non-aviation 155 158 141 $ 5,103 $ 5,223 $ 3,811 The following table reconciles EBITDA As Defined by segment to consolidated income from continuing operations before income taxes (in millions): Fiscal Years Ended September 30, 2020 2019 2018 EBITDA As Defined Power & Control $ 1,345 $ 1,395 $ 1,115 Airframe 955 1,063 759 Non-aviation 54 51 44 Total segment EBITDA As Defined 2,354 2,509 1,918 Unallocated corporate expenses 76 90 41 Total Company EBITDA As Defined 2,278 2,419 1,877 Depreciation and amortization 283 225 129 Interest expense - net 1,029 859 663 Acquisition-related costs 31 169 29 Stock compensation expense 93 93 58 Refinancing costs 28 3 6 COVID-19 pandemic & 737 MAX restructuring costs 54 — — Other, net 20 7 6 Income from continuing operations before income taxes $ 740 $ 1,063 $ 986 The following table presents capital expenditures and depreciation and amortization by segment (in millions): Fiscal Years Ended September 30, 2020 2019 2018 Capital expenditures Power & Control $ 89 $ 50 $ 39 Airframe 10 48 32 Non-aviation 4 3 2 Corporate 2 1 — $ 105 $ 102 $ 73 Depreciation and amortization Power & Control $ 117 $ 99 $ 67 Airframe 157 119 56 Non-aviation 7 6 5 Corporate 2 2 1 $ 283 $ 226 $ 129 The following table presents total assets by segment (in millions): September 30, 2020 September 30, 2019 Total assets Power & Control $ 7,005 $ 7,037 Airframe 6,575 6,672 Non-aviation 251 262 Corporate 4,564 1,322 Assets of discontinued operations (Note 23) — 962 $ 18,395 $ 16,255

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION The Company’s equity compensation plans are designed to assist the Company in attracting, retaining, motivating and rewarding key employees, directors or consultants, and promoting the creation of long-term value for stockholders by closely aligning the interests of these individuals with those of the Company’s stockholders. The Company’s equity compensation plans provide for the granting of stock options. Non-cash stock compensation expense recognized by the Company during the fiscal years ended September 30, 2020, 2019 and 2018 was $92.7 million, $93.4 million and $58.5 million, respectively. The weighted-average grant date fair value of options granted during the fiscal years ended September 30, 2020, 2019 and 2018 was $157.41, $114.43 and $81.04, respectively. Compensation expense is recognized based upon probability assessments of awards that are expected to vest in future periods, adjusted for expected forfeitures. Such probability assessments are subject to revision and, therefore, unrecognized compensation expense is subject to future changes in estimate. As of September 30, 2020, there was approximately $62.8 million of total unrecognized compensation expense related to non-vested awards expected to vest, which is expected to be recognized over a weighted-average period of 1.7 years. On September 25, 2020, the Compensation Committee of the Board of Directors determined to allow the portion of options granted in fiscal 2020 with a scheduled vesting date in 2020 to vest, effective September 30, 2020, notwithstanding that performance criteria for such options would not be met. This action impacts options granted to approximately 85 individuals, including all of the independent directors and certain executive officers. This action was treated as a modification for accounting purposes under ASC 718. An additional $2.5 million of stock compensation expense for fiscal 2020 resulted from this modification. The fair value of the Company’s employee stock options was estimated at the date of grant or modification using a Black-Scholes option-pricing model with the following weighted average assumptions for all options granted during the fiscal years ended: Fiscal Years Ended September 30, 2020 2019 2018 Risk-free interest rate 0.26% to 1.65% 2.33% to 3.03% 2.01% to 2.84% Expected life of options 5 to 5.5 years 5.5 years 5.2 years Expected dividend yield of stock — — — Expected volatility of stock 25% to 39% 25% 25% The risk-free interest rate is based upon the Treasury bond rates as of the grant or modification date. The average expected life of stock-based awards is based on the Company’s actual historical exercise experience. Expected volatility of stock was calculated using a rate based upon the historical volatility of TransDigm’s common stock up to the date of grant or date of modification. The Company estimates stock option forfeitures based on historical data. The total number of stock options expected to vest is adjusted by actual and estimated forfeitures. Changes to the actual and estimated forfeitures will result in a cumulative adjustment in the period of change. Notwithstanding the special cash dividends declared and paid from time to time, the Company historically has not declared and paid regular cash dividends and does not anticipate declaring and paying regular cash dividends in future periods; thus, no dividend rate assumption is used. The total fair value of options vested during fiscal years ended September 30, 2020, 2019 and 2018 was $97.2 million, $37.7 million and $44.4 million, respectively. The significant increase in the total fair value of options vested during fiscal year 2020 compared to fiscal years 2019 and 2018 resulted from substantially more options vesting and an increase in the fair value of options granted during the current fiscal year. 2019 Stock Option Plan In August 2019, the Board of Directors of TD Group adopted a new stock option plan, which was subsequently approved by stockholders on October 3, 2019. The 2019 stock option plan permits TD Group to award stock options to our key employees, directors or consultants. The total number shares of TD Group common stock reserved for issuance or delivery under the 2019 stock option plan is 4,000,000, subject to adjustment in the event of any stock dividend or split, reorganization, recapitalization, merger, share exchange or any other similar corporate transaction or event. No grants have been made from TD Group’s 2019 stock option plan as of September 30, 2020. 2014 Stock Option Plan In July 2014, the Board of Directors of TD Group adopted the 2014 stock option plan, which was subsequently approved by stockholders on October 2, 2014. The 2014 stock option plan permits TD Group to award our key employees, directors or consultants stock options. The total number of shares of TD Group common stock reserved for issuance or delivery under the 2014 stock option plan is 5,000,000, subject to adjustment in the event of any stock dividend or split, reorganization, recapitalization, merger, share exchange or any other similar corporate transaction or event. Performance Vested Stock Options —Generally all of the options granted through September 30, 2020 under the 2014 stock option plan have been pursuant to an equity incentive program adopted by the Company in 2008. Under the 2008 equity incentive program, generally all of the options granted will vest based on the Company’s achievement of established operating performance goals. As of September 30, 2020, the Company projected that the performance criteria is not expected to be acheived on the portion of options granted in fiscal 2020 with a scheduled vesting date of September 30, 2021 and beyond. The following table summarizes the activity, pricing and other information for the Company’s performance vested stock-based award activity during the fiscal year ended September 30, 2020: Number of Weighted-Average Weighted-Average Aggregate Outstanding at September 30, 2019 3,167,458 $ 323.73 Granted 742,840 538.92 Exercised (34,495) 284.21 Forfeited (261,946) 372.81 Expired — — Outstanding at September 30, 2020 3,613,857 $ 364.79 7.6 years $ 398,716,843 Expected to vest 1,235,922 $ 332.98 7.5 years $ 175,676,981 Exercisable at September 30, 2020 1,709,551 $ 336.58 7.2 years $ 236,841,196 At September 30, 2020, there were 1,316,998 remaining shares available for award under TD Group’s 2014 stock option plan. 2006 Stock Incentive Plan In conjunction with the consummation of the Company’s initial public offering, a 2006 stock incentive plan was adopted by TD Group. In July 2008 and March 2011, the plan was amended to increase the number of shares available for issuance thereunder. TD Group reserved 8,119,668 shares of its common stock for issuance to key employees, directors or consultants under the plan. Awards under the plan were in the form of options, restricted stock or other stock-based awards. Options granted under the plan expire no later than the tenth anniversary of the applicable date of grant of the options, and have an exercise price of not less than the fair market value of our common stock on the date of grant. Restricted stock granted under the plan vested over three years. No restricted stock units remained outstanding as of September 30, 2018. Performance Vested Stock Options —All of the options granted under the 2006 stock incentive plan have been pursuant to an equity incentive program adopted by the Company in 2008. Under the 2008 equity incentive program, all of the options granted vest based on the Company’s achievement of established operating performance goals. The following table summarizes the activity, pricing and other information for the Company’s performance vested stock-based award activity during the fiscal year ended September 30, 2020: Number of Weighted-Average Weighted-Average Aggregate Outstanding at September 30, 2019 3,134,022 $ 155.34 Granted — — Exercised (887,842) 115.15 Forfeited (10,500) 226.34 Expired — — Outstanding at September 30, 2020 2,235,680 $ 170.97 3.4 years $ 679,982,072 Exercisable at September 30, 2020 2,235,680 $ 170.97 3.4 years $ 679,982,072 The 2006 stock incentive plan expired on March 14, 2016 and no further shares were granted under the plan thereafter. 2003 Stock Option Plan Certain executives and key employees of the Company were granted stock options under TD Group’s 2003 stock option plan. All shares had been issued as of September 30, 2013. As of September 30, 2020 and 2019, 829 and 77,829 options were outstanding and exercisable at a weighted average price per option of $130.09. As of September 30, 2020, the weighted average remaining contractual term of the 829 options outstanding and exercisable is 2.1 years and the aggregate intrinsic value is $0.3 million. The total intrinsic value of performance options exercised during the fiscal years ended September 30, 2020, 2019 and 2018 was $394.2 million, $240.2 million and $192.5 million, respectively. Dividend Equivalent Plans Pursuant to the Third Amended and Restated TransDigm Group Incorporated 2003 Stock Option Plan Dividend Equivalent Plan, the Second Amended and Restated TransDigm Group Incorporated 2006 Stock Incentive Plan Dividend Equivalent Plan and the 2014 Stock Option Plan Dividend Equivalent Plan, all of the options granted under the existing stock option plans are entitled to certain dividend equivalent payments in the event of the declaration of a dividend by the Company. Dividend equivalent payments on vested options were $184.9 million, $111.0 million and $56.1 million during the fiscal years ended September 30, 2020, 2019 and 2018, respectively. At September 30, 2020, there was $72.4 million recorded in accrued liabilities and $49.0 million accrued in other non-current liabilities on the consolidated balance sheets related to future dividend equivalent payments.

LEASES

LEASES	12 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Leases of Lessee Disclosure	LEASES The Company leases certain manufacturing facilities, offices, land, equipment and vehicles. Such leases, some of which are noncancellable and, in many cases, include renewals, expire at various dates. Such options to renew are included in the lease term when it is reasonably certain that the option will be exercised. The Company’s lease agreements typically do not contain any significant residual value guarantees or restrictive covenants, and payments within certain lease agreements are adjusted periodically for changes in an index or rate. The Company determines if an arrangement is a lease at inception. Operating lease assets and liabilities are recognized at the commencement date of the lease based on the present value of lease payments over the lease term. Lease assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. The discount rate implicit within our leases is generally not determinable and therefore we determine the discount rate based on our incremental borrowing rate. The incremental borrowing rate for our leases is determined based on the lease term and the currency in which lease payments are made. The length of a lease term includes options to extend or terminate the lease when it is reasonably certain that the Company will exercise those options. The Company made an accounting policy election to not recognize lease assets or liabilities for leases with a term of 12 months or less. Additionally, when accounting for leases, the Company combines payments for leased assets, related services and other components of a lease. The components of lease expense for the fiscal year ended September 30, 2020 are as follows (in millions): Classification Fiscal Year Ended September 30, 2020 Operating lease cost Cost of Sales or Selling and Administrative Expenses $ 29 Finance lease cost Amortization of leased assets Cost of Sales 3 Interest on lease liabilities Interest Expense - Net 4 Total lease cost $ 36 Supplemental cash flow information related to leases for the fiscal year ended September 30, 2020 is as follows (in millions): Fiscal Year Ended September 30, 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash outflows from operating leases $ 29 Operating cash outflows from finance leases 4 Financing cash outflows from finance leases 2 Lease assets obtained in exchange for new lease obligations: Operating leases $ 32 Supplemental balance sheet information related to leases is as follows (in millions): Classification September 30, 2020 Operating Leases Operating lease right-of-use assets Other Assets $ 103 Current operating lease liabilities Accrued Liabilities 22 Long-term operating lease liabilities Other Non-current Liabilities 87 Total operating lease liabilities $ 109 Finance Leases Finance lease right-of-use assets, net Property, Plant and Equipment—Net $ 67 Current finance lease liabilities Accrued Liabilities 2 Long-term finance lease liabilities Other Non-current Liabilities 55 Total finance lease liabilities $ 57 As of September 30, 2020, the Company has the following remaining lease term and weighted average discount rates: Weighted-average remaining lease term Operating leases 6.5 years Finance leases 16.4 years Weighted-average discount rate Operating leases 6.2% Finance leases 7.2% Maturities of lease liabilities at September 30, 2020 are as follows (in millions): Operating Leases Finance Leases 2021 $ 28 $ 6 2022 24 6 2023 19 6 2024 16 6 2025 13 6 Thereafter 35 70 Total future minimum lease payments 135 100 Less: imputed interest 26 43 Present value of lease liabilities reported $ 109 $ 57 Rental expense during the fiscal years ended September 30, 2019 and September 30, 2018 was $26 million and $19 million, respectively. Future minimum rental commitments at September 30, 2019 under operating leases having initial or remaining non-cancellable lease terms exceeding one year are $22 million in fiscal 2020, $32 million in fiscal 2021, $17 million in fiscal 2022, $14 million in fiscal 2023, $13 million in fiscal 2024 and $28 million thereafter.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The following tables present our assets and liabilities that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy. The fair value hierarchy has three levels based on the reliability of the inputs used to determine fair value. Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and inputs (other than quoted prices) that are observable for the asset or liability, either directly or indirectly. Level 3 inputs are unobservable inputs for the asset or liability. A financial asset or liability’s classification within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement. The following summarizes the carrying amounts and fair values of financial instruments (in millions): September 30, 2020 September 30, 2019 Level Carrying Fair Value Carrying Fair Value Assets: Cash and cash equivalents 1 $ 4,717 $ 4,717 $ 1,467 $ 1,467 Interest rate cap agreements (1) 2 — — 1 1 Liabilities: Interest rate swap agreements (2) 2 56 56 13 13 Interest rate swap agreements (3) 2 328 328 202 202 Foreign currency forward exchange contracts (3) 2 1 1 6 6 Short-term borrowings - trade receivable securitization facility (4) 1 349 349 350 350 Long-term debt, including current portion: Term loans (4) 2 7,378 7,004 7,449 7,478 Revolving credit facility (4) 2 200 200 — — 2022 Notes (4) 1 — — 1,146 1,167 2024 Notes (4) 1 1,195 1,194 1,194 1,239 2025 Notes (4) 1 750 743 750 782 2025 Secured Notes (4) 1 1,091 1,194 — — 6.375% 2026 Notes (4) 1 944 948 943 999 6.875% 2026 Notes (4) 1 493 500 491 535 6.25% 2026 Notes (4) 1 4,350 4,604 3,942 4,290 7.50% 2027 Notes (4) 1 545 569 545 595 5.50% 2027 Notes (4) 1 2,629 2,544 — — Government refundable advances 2 28 28 39 39 Finance lease obligations 2 57 57 50 50 (1) Included in other non-current assets on the consolidated balance sheets. (2) Included in accrued liabilities on the consolidated balance sheets. (3) Included in other non-current liabilities on the consolidated balance sheets. (4) The carrying amount of the debt instrument is presented net of the debt issuance costs, premium and discount. Refer to Note 12, “Debt,” for gross carrying amounts. The Company values its financial instruments using an industry standard market approach, in which prices and other relevant information are generated by market transactions involving identical or comparable assets or liabilities. No financial instruments were recognized using unobservable inputs. Interest rate swaps were measured at fair value using quoted market prices for the swap interest rate indexes over the term of the swap discounted to present value versus the fixed rate of the contract. The interest rate caps were measured at fair value using implied volatility rates of each individual caplet and the yield curve for the related periods. The Company’s derivative contracts consist of foreign currency exchange contracts and, from time to time, interest rate swap and cap agreements. These derivative contracts are over-the-counter, and their fair value is determined using modeling techniques that include market inputs such as interest rates, yield curves, and currency exchange rates. These contracts are categorized as Level 2 in the fair value hierarchy. The estimated fair value of the Company’s term loans was based on information provided by the agent under the Company’s senior secured credit facility. The estimated fair values of the Company’s notes were based upon quoted market prices. There has not been any impact to the fair value of derivative liabilities due to the Company's own credit risk. Similarly, there has not been any impact to the fair value of derivative assets based on the Company's evaluation of counterparties' credit risks.

DERIVATIVES AND HEDGING ACTIVIT

DERIVATIVES AND HEDGING ACTIVITIES	12 Months Ended
	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVES AND HEDGING ACTIVITIES	DERIVATIVES AND HEDGING ACTIVITIES The Company is exposed to, among other things, the impact of changes in foreign currency exchange rates and interest rates in the normal course of business. The Company’s risk management program is designed to manage the exposure and volatility arising from these risks, and utilizes derivative financial instruments to offset a portion of these risks. The Company uses derivative financial instruments only to the extent necessary to hedge identified business risks and does not enter into such transactions for trading purposes. The Company generally does not require collateral or other security with counterparties to these financial instruments and is therefore subject to credit risk in the event of nonperformance; however, the Company monitors credit risk and currently does not anticipate nonperformance by other parties. These derivative financial instruments do not subject the Company to undue risk, as gains and losses on these instruments generally offset gains and losses on the underlying assets, liabilities, or anticipated transactions that are being hedged. The Company has agreements with each of its swap and cap counterparties that contain a provision whereby if the Company defaults on the credit facility the Company could also be declared in default on its swaps and caps, resulting in an acceleration of payment under the swaps and caps. All derivative financial instruments are recorded at fair value in the consolidated balance sheets. For a derivative that has not been designated as an accounting hedge, the change in the fair value is recognized immediately through earnings. For a derivative that has been designated as an accounting hedge of an existing asset or liability (a fair value hedge), the change in the fair value of both the derivative and underlying asset or liability is recognized immediately through earnings. For a derivative designated as an accounting hedge of an anticipated transaction (a cash flow hedge), the change in the fair value is recorded on the consolidated balance sheet in accumulated other comprehensive income to the extent the derivative is effective in mitigating the exposure related to the anticipated transaction. The change in the fair value related to the ineffective portion of the hedge, if any, is immediately recognized in earnings. The amount recorded within accumulated other comprehensive income is reclassified into earnings in the same period during which the underlying hedged transaction affects earnings. Interest Rate Swap and Cap Agreements – Interest rate swap and cap agreements are used to manage interest rate risk associated with floating-rate borrowings under our credit facility. The interest rate swap and cap agreements utilized by the Company effectively modify the Company’s exposure to interest rate risk by converting a portion of the Company’s floating-rate debt to a fixed rate basis through the expiration date of the interest rate swap and cap agreements, thereby reducing the impact of interest rate changes on future interest expense. These agreements involve the receipt of floating rate amounts in exchange for fixed rate interest payments over the term of the agreements without an exchange of the underlying principal amount. These derivative instruments qualify as effective cash flow hedges under U.S. GAAP. For these cash flow hedges, the effective portion of the gain or loss from the financial instruments was initially reported as a component of accumulated other comprehensive loss in stockholders’ deficit and subsequently reclassified into earnings in the same line as the hedged item in the same period or periods during which the hedged item affected earnings. As the interest rate swap and cap agreements are used to manage interest rate risk, any gains or losses from the derivative instruments that are reclassified into earnings are recognized in interest expense - net in the consolidated statements of income. The following table summarizes the Company’s interest rate swap agreements: Aggregate Notional Amount Start Date End Date Related Term Loans Conversion of Related Variable Rate Debt to Fixed Rate of: $500 6/29/2018 3/31/2025 Tranche E 5.25% (3.0% plus the 2.25% margin percentage) $750 6/30/2020 6/30/2022 Tranche E 4.75% (2.5% plus the 2.25% margin percentage) $1,500 6/30/2022 3/31/2025 Tranche E 5.35% (3.1% plus the 2.25% margin percentage) $1,000 6/28/2019 12/9/2025 Tranche F 4.05% (1.8% plus the 2.25% margin percentage) $1,400 6/30/2021 12/9/2025 Tranche F 5.25% (3.0% plus the 2.25% margin percentage) $500 12/30/2016 12/31/2021 Tranche G 4.15% (1.9% plus the 2.25% margin percentage) $400 9/30/2017 9/30/2022 Tranche G 4.15% (1.9% plus the 2.25% margin percentage) $900 12/31/2021 6/28/2024 Tranche G 5.35% (3.1% plus the 2.25% margin percentage) $400 9/30/2022 6/28/2024 Tranche G 5.25% (3.0% plus the 2.25% margin percentage) The following table summarizes the Company’s interest rate cap agreements: Aggregate Notional Amount Start Date End Date Related Debt Offsets Variable Rate Debt Attributable to Fluctuations Above: $750 6/30/2020 6/30/2022 Tranche E Three month LIBOR of 2.5% $400 6/30/2016 6/30/2021 Tranche F Three month LIBOR of 2.0% $400 12/30/2016 12/31/2021 Tranche G Three month LIBOR of 2.5% Certain derivative asset and liability balances are offset where master netting agreements provide for the legal right of setoff. For classification purposes, we record the net fair value of each type of derivative position that is expected to settle in less than one year with each counterparty as a net current asset or liability and each type of long-term position as a net non-current asset or liability. The amounts shown in the table below represent the gross amounts of recognized assets and liabilities, the amounts offset in the consolidated balance sheet and the net amounts of assets and liabilities presented therein. September 30, 2020 September 30, 2019 Asset Liability Asset Liability Interest rate cap agreements $ — $ — $ 1 $ — Interest rate swap agreements (1) — (384) — (216) Net derivatives as classified in the balance sheet (2) $ — $ (384) $ 1 $ (216) (1) The increase in the interest rate swap liability is primarily attributable to a downward trend in LIBOR during fiscal 2020. (2) Refer to Note 20, "Fair Value Measurements," for the consolidated balance sheet classification of our interest rate swap and cap agreements. Based on the fair value amounts of the interest rate swap and cap agreements determined as of September 30, 2020, the estimated net amount of existing gains and losses and caplet amortization expected to be reclassified into interest expense within the next twelve months is approximately $10.3 million. During the fourth quarter of fiscal 2020, the $750 million notional amount interest rate swap agreement and the $750 million notional amount interest rate cap agreement, both with maturity dates of June 30, 2020, were settled. Upon the settlement of both agreements, the Company recognized interest expense of $2.2 million. Foreign Currency Forward Exchange Contracts – The Company transacts business in various foreign currencies, which subjects the Company’s cash flows and earnings to exposure related to changes in foreign currency exchange rates. These exposures arise primarily from purchases or sales of products and services from third parties. Foreign currency forward exchange contracts provide for the purchase or sale of foreign currencies at specified future dates at specified exchange rates, and are used to offset changes in the fair value of certain assets or liabilities or forecasted cash flows resulting from transactions denominated in foreign currencies. At September 30, 2020, the Company had outstanding foreign currency forward exchange contracts principally to sell U.S. dollars with notional amounts of $172.5 million. These notional values consist primarily of contracts for the Canadian dollar and European euro and are stated in U.S. dollar equivalents at spot exchange rates at the respective dates. During the fiscal year ended September 30, 2020, the Company recognized losses on foreign currency forward exchange contracts designated as fair value hedges of $1.6 million in other (income) expense on the consolidated statements of income. During the fiscal year ended September 30, 2020, the Company recognized losses on foreign currency forward exchange contracts designated as cash flow hedges of $3.9 million in net sales on the consolidated statements of income. The losses were previously recorded as a component of accumulated other comprehensive (loss) income in stockholders' deficit. During the fiscal year ended September 30, 2020, the Company recorded a loss of $0.7 million on foreign currency forward exchange contracts that have not been designated as accounting hedges. These foreign currency exchange losses are included in selling and administrative expenses. Amounts related to foreign currency forward exchange contracts included in accumulated other comprehensive (loss) income in stockholders' deficit are reclassified into earnings when the hedged transaction settles. The Company expects to reclassify approximately $1.2 million of net losses into earnings over the next 12 months. The maximum duration of the Company’s foreign currency cash flow hedge contracts at September 30, 2020 was 12 months.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	12 Months Ended
	Sep. 30, 2020
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME The following table presents the components of accumulated other comprehensive (loss) income, net of taxes, for the fiscal years ended September 30, 2020, 2019 and 2018 (in millions): Unrealized (loss) gain on derivatives designated and qualifying as cash flow hedges (1) Defined benefit pension plan activity (2) Currency translation adjustment Total Balance at September 30, 2018 $ 67 $ (11) $ (52) $ 4 Cumulative effect of ASU 2018-02, adopted October 1, 2018 (2) — — (2) Current-period other comprehensive loss (241) (29) (115) (385) Amounts reclassified from AOCI related to derivative instruments 4 — — 4 Net current-period other comprehensive loss (239) (29) (115) (383) Balance at September 30, 2019 (172) (40) (167) (379) Current-period other comprehensive (loss) gain (130) 32 76 (22) Balance at September 30, 2020 $ (302) $ (8) $ (91) $ (401) (1) Unrealized (loss) gain represents derivative instruments, net of taxes of $36, $70 and $(34) for the fiscal years ended September 30, 2020, 2019 and 2018, respectively. (1) Defined benefit pension plan and other post-retirement plan activity represents pension liability adjustments, net of taxes of $(1), $9 and $(1) for the fiscal years ended September 30, 2020, 2019 and 2018, respectively. A summary of reclassifications out of accumulated other comprehensive (loss) income for the fiscal years ended September 30, 2020 and 2019 is provided below (in millions): Amount Reclassified Fiscal Years Ended September 30, Description of reclassifications out of accumulated other comprehensive (loss) income 2020 2019 Amortization from redesignated interest rate swap and cap agreements (1) $ 4 $ 3 Losses from settlement of foreign currency forward exchange contracts (2) (4) — Deferred tax expense on reclassifications out of accumulated other comprehensive (loss) income — 1 Losses reclassified into earnings, net of tax $ — $ 4 (1) This component of accumulated other comprehensive (loss) income is included in interest expense. Refer to Note 21, “Derivatives and Hedging Activities,” for additional information. (2) This component of accumulated other comprehensive (loss) income is included in net sales. Refer to Note 21, “Derivatives and Hedging Activities,” for additional information.

DISCONTINUED OPERATIONS

DISCONTINUED OPERATIONS	12 Months Ended
	Sep. 30, 2020
DISCONTINUED OPERATIONS [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	DISCONTINUED OPERATIONS The table below summarizes income (loss) from discontinued operations, net of tax, for the fiscal years ended September 30, 2020, 2019 and 2018 (in millions): Fiscal Year Ended September 30, 2020 2019 2018 Net sales $ 79 $ 294 $ 12 Income (loss) from discontinued operations, before income taxes 11 — — Income tax provision (benefit) 4 (13) (2) Income from discontinued operations, net of tax 7 13 2 Gain (loss) from sale of discontinued operations, net of tax 40 38 (7) Income (loss) from discontinued operations, net of tax $ 47 $ 51 $ (5) Fiscal Year 2020 Divestitures & Discontinued Operations On December 20, 2019, TransDigm completed the divestiture of Souriau-Sunbank to Eaton for approximately $920 million. Souriau-Sunbank was acquired by TransDigm as part of its acquisition of Esterline in March 2019 and was included in TransDigm’s Non-aviation segment. The divestiture represented a strategic shift in TransDigm’s business and, in accordance with U.S. GAAP, qualified as discontinued operations. Therefore, the results of operations of Souriau-Sunbank are presented in discontinued operations in the accompanying consolidated financial statements for all periods presented since the date acquired. Income from discontinued operations, net of tax, for the fiscal year ended September 30, 2020 was $47 million. This was comprised of $7 million income from Souriau-Sunbank's operations and a gain on the sale of Souriau-Sunbank of $40 million. Fiscal Year 2019 Divestitures & Discontinued Operations On September 20, 2019, TransDigm completed the divestiture of its EIT group of businesses to an affiliate of KPS Capital Partners, LP for approximately $190 million. EIT was acquired by TransDigm as part of its acquisition of Esterline Technologies Corporation in March 2019 and was included in TransDigm’s Non-aviation segment. The divestiture represented a strategic shift in TransDigm’s business and, in accordance with U.S. GAAP, qualified as discontinued operations. Therefore, the results of operations of EIT were presented in discontinued operations in the accompanying consolidated financial statements for all periods presented since the date acquired. Income from discontinued operations, net of tax, was $51 million for the fiscal year ended September 30, 2019. This included income from operations of $13 million related to EIT and Souriau-Sunbank and a gain on the sale of EIT of $38 million. Souriau-Sunbank’s net sales, loss from discontinued operations (before income tax) and income tax benefit were $199 million, $17 million and $14 million, respectively, for the fiscal year ended September 30, 2019. EIT’s net sales, income from discontinued operations (before income tax) and income tax expense were $95 million, $17 million and $1 million, respectively, for the fiscal year ended September 30, 2019. Cash related to discontinued operations, which was excluded from the consolidated statement of cash flows, included net cash provided by operating activities of $35 million and net cash used in investing activities of $11 million. Fiscal Year 2018 Divestitures & Discontinued Operations On January 26, 2018, the Company completed the sale of Schroth in a management buyout to a private equity fund and certain members of Schroth management for approximately $61 million. The Company previously acquired Schroth in February 2017. The results of operations of Schroth are presented in discontinued operations in the accompanying consolidated financial statements for the fiscal year ended September 30, 2018. The loss from discontinued operations, net of tax, was approximately $5 million in the consolidated statement of income for the fiscal year ended September 30, 2018. Assets and Liabilities Held for Sale - Souriau-Sunbank At September 30, 2019, Souriau-Sunbank’s assets held-for-sale and liabilities held-for-sale were $962 million and $157 million, respectively. Under U.S. GAAP, assets held for sale are to be reported at lower of its carrying amount or fair value less cost to sell. The following is the summarized balance sheet of Souriau-Sunbank’s assets held-for-sale and liabilities held-for-sale as of September 30, 2019 (in millions): Assets and Liabilities of Discontinued Operations Held-for-Sale Fiscal Year Ended September 30, 2019 Cash and cash equivalents $ 29 Trade accounts receivable—Net 67 Inventories—Net 88 Prepaid expenses and other 2 Property, plant and equipment—Net 101 Goodwill 480 Other intangibles—Net 194 Other 1 Total assets of discontinued operations $ 962 Accounts payable $ 33 Accrued liabilities 55 Long-term debt 6 Deferred income taxes 42 Other 21 Total liabilities of discontinued operations $ 157

QUARTERLY FINANCIAL DATA (UNAUD

QUARTERLY FINANCIAL DATA (UNAUDTIED)	12 Months Ended
	Sep. 30, 2020
Quarterly Financial Information Disclosure [Abstract]
QUARTERLY FINANCIAL DATA (UNAUDITED)	QUARTERLY FINANCIAL DATA (UNAUDITED) First Quarter Second Quarter Third Quarter Fourth Quarter (in millions, except per share amounts) Fiscal Year Ended September 30, 2020 (1) Net sales (2) $ 1,465 $ 1,443 $ 1,022 $ 1,173 Gross profit (2) 801 818 491 536 Income (Loss) from continuing operations, net of tax (2) 234 323 (5) 101 Income (Loss) from discontinued operations, net of tax (2) 71 (4) (1) (19) Less: Net income attributable to noncontrolling interests (2) (1) — — — Net income (loss) attributable to TD Group (2) $ 304 $ 319 $ (6) $ 82 Net income (loss) attributable to TD Group common stockholders (3) $ 119 $ 319 $ (6) $ 82 Earnings (Loss) per share from continuing operations—basic and diluted (4) $ 0.83 $ 5.63 $ (0.09) $ 1.76 Earnings (Loss) per share from discontinued operations—basic and diluted (4) 1.24 (0.07) (0.01) (0.33) Earnings (Loss) per share (4) $ 2.07 $ 5.56 $ (0.10) $ 1.43 First Quarter Second Quarter Third Quarter Fourth Quarter (in millions, except per share amounts) Fiscal Year Ended September 30, 2019 (1) Net sales (2) $ 993 $ 1,168 $ 1,521 $ 1,541 Gross profit (2) 564 650 713 882 Income from continuing operations, net of tax (2) 196 200 128 317 Income from discontinued operations, net of tax (2) — 2 17 32 Less: Net income attributable to noncontrolling interests (2) — — — (2) Net income attributable to TD Group (2) $ 196 $ 202 $ 145 $ 347 Net income attributable to TD Group common stockholders (3) $ 172 $ 202 $ 145 $ 260 Earnings per share from continuing operations—basic and diluted (4) $ 3.05 $ 3.56 $ 2.27 $ 4.08 Earnings per share from discontinued operations—basic and diluted (4) — 0.04 0.30 0.55 Earnings per share (4) $ 3.05 $ 3.60 $ 2.57 $ 4.63 (1) Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Souriau-Sunbank and EIT at September 30, 2019, as discontinued operations. Refer to Note 23, “Discontinued Operations,” for additional information. (2) The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. Refer to Note 2 “Acquisitions and Divestitures,” for additional information. (3) Net income applicable to TD Group common stockholders represents net income attributable to TD Group less special dividends and dividend equivalent payments. Special dividend and dividend equivalent payments were $185 million, $24 million and $87 million, respectively, for the first quarter ended December 28, 2019, first quarter ended December 29, 2018 and fourth quarter ended September 30, 2019. (4) The sum of the earnings per share for the four quarters in a year does not necessarily equal the total year earnings per share due to the weighted average number of shares outstanding in each quarter.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Sep. 30, 2020
Subsequent Event [Line Items]
Subsequent Events [Text Block]	SUBSEQUENT EVENTSOn October 26, 2020, the Company repaid $200 million of the revolving credit facility, in addition to $0.5 million of accrued interest.

VALUATION AND QUALIFYING ACCOUN

VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Sep. 30, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
VALUATION AND QUALIFYING ACCOUNTS	TRANSDIGM GROUP INCORPORATED VALUATION AND QUALIFYING ACCOUNTS FOR THE FISCAL YEARS ENDED SEPTEMBER 30, 2020, 2019, AND 2018 (Amounts in millions) Column A Column B Column C Column D Column E Balance at Additions Deductions from Reserve (1) Balance at Description Charged to Costs Acquisitions & Purchase Price Adjustments Fiscal Year Ended September 30, 2020 Allowance for uncollectible accounts $ 17 $ 21 $ 3 $ (4) $ 37 Inventory valuation reserves 124 34 37 (17) 178 Valuation allowance for deferred tax assets 118 15 (1) — 132 Fiscal Year Ended September 30, 2019 Allowance for uncollectible accounts $ 5 $ 5 $ 9 $ (2) $ 17 Reserve for excess and obsolete inventory 99 17 17 (9) 124 Valuation allowance for deferred tax assets 47 40 31 — 118 Fiscal Year Ended September 30, 2018 Allowance for uncollectible accounts $ 4 $ 2 $ 1 $ (2) $ 5 Reserve for excess and obsolete inventory 80 15 11 (11) 95 Valuation allowance for deferred tax assets 33 14 — — 47 (1) The amounts in this column represent charge-offs net of recoveries and the impact of foreign currency translation adjustments.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis Of Presentation And Consolidation	Basis of Presentation and Consolidation—The accompanying consolidated financial statements were prepared in conformity with U.S. GAAP and include the accounts of TD Group and subsidiaries. All significant intercompany balances and transactions have been eliminated.
Revenue from Contract with Customer	Revenue Recognition —Revenue is recognized from the sale of products when control transfers to the customer, which is demonstrated by our right to payment, a transfer of title, a transfer of the risk and rewards of ownership, or the customer acceptance, but most frequently upon shipment where the customer obtains physical possession of the goods. The majority of the Company's revenue is recorded at a point in time. Sales recognized over time are generally accounted for using an input measure to determine progress completed at the end of the period. Sales for service contracts generally are recognized as the services are provided. Refer to Note 5, “Revenue Recognition,” for additional information regarding the Company’s revenue recognition policy. Shipping and Handling Costs —Shipping and handling costs are included in cost of sales in the consolidated statements of income.
Research and Development Costs	Research and Development Costs —The Company expenses research and development costs as incurred and classifies such amounts in selling and administrative expenses. The expense recognized for research and development costs for the fiscal years ended September 30, 2020, 2019 and 2018 was approximately $130.9 million, $116.8 million, and $73.8 million, respectively.
Cash Equivalents	Cash Equivalents —The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents.
Allowance For Uncollectible Accounts	Allowance for Uncollectible Accounts —The Company reserves for amounts determined to be uncollectible based on specific identification of losses and estimated losses based on historical experience. The allowance also incorporates a provision for the estimated impact of disputes with customers. The determination of the amount of the allowance for uncollectible accounts is subject to judgment and estimation by management. If circumstances change or economic conditions deteriorate or improve, the allowance for uncollectible accounts could increase or decrease.
Inventories	Inventories—Inventories are stated at the lower of cost or net realizable value. Cost of inventories is generally determined by the average cost and the first-in, first-out (“FIFO”) methods and includes material, labor and overhead related to the manufacturing process. Provision for potentially obsolete or slow-moving inventory is made based on management’s analysis of inventory levels and future sales forecasts.
Property, Plant and Equipment	Property, Plant and Equipment —Property, plant and equipment are stated at cost and include improvements which significantly increase capacities or extend the useful lives of existing plant and equipment. Depreciation is computed using the straight-line method over the following estimated useful lives: land improvements from 10 to 20 years, buildings and improvements from 5 to 30 years, machinery and equipment from 2 to 10 years and furniture and fixtures from 3 to 10 years. Net gains or losses related to asset dispositions are recognized in earnings in the period in which dispositions occur. Routine maintenance, repairs and replacements are expensed as incurred. Amortization expense of assets accounted for as finance leases is included within depreciation expense. Property, plant and equipment is assessed for potential impairment whenever indicators of impairment are present by determining whether the carrying value of the property can be recovered through projected, undiscounted cash flows from future operations over the property’s remaining estimated useful life. Any impairment recognized is the amount by which the carrying amount exceeds the fair value of the asset. Fair value is measured based on quoted market prices in active markets, if available. If quoted market prices are not available, the estimate of fair value is based on various valuation techniques, including the discounted value of estimated future cash flows.
Debt Issue Costs, Premiums and Discounts	Debt Issuance Costs, Premiums and Discounts —The cost of obtaining financing as well as premiums and discounts are amortized using the effective interest method over the terms of the respective obligations as a component of interest expense within the consolidated statements of income. Debt issuance costs are presented in the consolidated balance sheets as a direct reduction from the carrying amount of the related debt liabilities.
Financial Instruments	Financial Instruments —Interest rate swap and cap agreements are used to manage interest rate risk associated with floating-rate borrowings under our credit facility. The interest rate swap and cap agreements utilized by the Company effectively modify the Company’s exposure to interest rate risk by converting a portion of the Company’s variable rate debt to a fixed rate basis through the expiration date of the interest rate swap and cap agreements, thereby reducing the impact of interest rate volatility on future interest expense. These agreements involve the receipt of variable rate amounts in exchange for fixed rate interest payments over the term of the agreements without an exchange of the underlying principal amount. These derivative instruments qualify as effective cash flow hedges under U.S. GAAP. The Company transacts business in various foreign currencies, which subjects the Company’s cash flows and results of operations to exposure related to changes in foreign currency exchange rates. These exposures arise primarily from purchases or sales of products and services from third parties. Foreign currency forward exchange contracts provide for the purchase or sale of foreign currencies at specified future dates at specified exchange rates, and are used to offset changes in the fair value of certain assets or liabilities or forecasted cash flows resulting from transactions denominated in foreign currencies. For the interest rate swap and cap agreements and the foreign currency forward contracts designated as cash flow hedges, the effective portion of the gain or loss from the financial instruments was initially reported as a component of accumulated other comprehensive loss in stockholders’ deficit and subsequently reclassified into earnings in the same line as the hedged item in the same period or periods during which the hedged item affected earnings. As the interest rate swap and cap agreements are used to manage interest rate risk, any gains or losses from the derivative instruments that are reclassified into earnings are recognized in interest expense - net in the consolidated statements of income. As the foreign currency forward exchange contracts are used to manage foreign currency exposure primarily arising from purchases or sales from third parties, any gains or losses from the derivative instruments that are reclassified into earnings are recognized in cost of sales or net sales in the consolidated statements of income.
Intangible Assets	Goodwill and Other Intangible Assets —In accordance with ASC 805, “Business Combinations,” the Company uses the acquisition method of accounting to allocate costs of acquired businesses to the assets acquired and liabilities assumed based on their estimated fair values at the dates of acquisition. The excess costs of acquired businesses over the fair values of the assets acquired and liabilities assumed were recognized as goodwill. The valuations of the acquired assets and liabilities assumed will impact the determination of future operating results. Determining the fair value of assets acquired and liabilities assumed requires management’s judgment and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash inflows and outflows, revenue growth rates, discount rates, customer attrition rates, royalty rates, asset lives and market multiples, among other items. We determine the fair values of intangible assets acquired generally in consultation with third-party valuation advisors. Fair value adjustments to the Company’s assets and liabilities are recognized and the results of operations of the acquired business are included in our consolidated financial statements from the effective date of the merger or acquisition. Intangible assets other than goodwill are recognized if the benefit of the intangible asset is obtained through contractual or other legal rights, or if the intangible asset can be sold, transferred, licensed or exchanged, regardless of the Company’s intent to do so. Goodwill is the excess of the purchase price paid over the estimated fair value of the net assets of a business acquired. Other intangible assets consist of identifiable intangibles acquired or recognized in accounting for the acquisitions (trademarks, trade names, technology, customer relationships, order backlog and other intangible assets). Goodwill and intangible assets that have indefinite useful lives (i.e., trademarks and trade names) are subject to annual impairment testing. Management determines fair value using a discounted future cash flow analysis or other accepted valuation techniques. The Company performs an annual impairment test for goodwill and other intangible assets as of the first day of the fourth fiscal quarter of each year, or more frequently, if an event occurs or circumstances change that would more likely than not reduce fair value below current value. At the time of goodwill impairment testing, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount, and whether it is therefore necessary to perform the quantitative goodwill impairment test. The quantitative goodwill impairment test consists of two steps. The first step of the goodwill impairment test, used to identify potential impairment, compares the fair value of a reporting unit (as defined) with its carrying amount, including goodwill. If the fair value of the reporting unit exceeds its carrying amount, goodwill is not considered impaired, and the second step of the goodwill impairment test is unnecessary. The second step measures the amount of impairment, if any, by comparing the carrying value of the goodwill associated with a reporting unit to the implied fair value of the goodwill derived from the estimated overall fair value of the reporting unit and the individual fair values of the other assets and liabilities of the reporting unit. U.S. GAAP requires that the annual, and any interim, impairment assessment be performed at the reporting unit level. The reporting unit level is one level below an operating segment. Substantially all goodwill was determined and recognized for each reporting unit pursuant to the accounting for the merger or acquisition as of the date of each transaction. With respect to acquisitions integrated into an existing reporting unit, any acquired goodwill is combined with the goodwill of the reporting unit. The impairment test for indefinite lived intangible assets consists of a comparison between their fair values and carrying values. If the carrying amounts of intangible assets that have indefinite useful lives exceed their fair values, an impairment loss will be recognized in an amount equal to the sum of any such excesses. The Company assesses the recoverability of its amortizable intangible assets only when indicators of impairment are present by determining whether the amortization over their remaining lives can be recovered through projected, undiscounted cash flows from future operations. Amortization of amortizable intangible assets is computed using the straight-line method over the following estimated useful lives: technology from 20 to 22 years, order backlog from 1 to 1.5 years, customer relationships over 20 years and other intangible assets over 20 years. Refer to Note 1, "Description of the Business and Impact of COVID-19 Pandemic," for further disclosures over the interim and annual impairment procedures performed during fiscal year 2020.
Stock-Based Compensation	Stock-Based Compensation —The Company records stock-based compensation expense using the Black-Scholes pricing model based on certain valuation assumptions. Compensation expense is recorded over the vesting periods of the stock options. The Company has classified stock-based compensation primarily within selling and administrative expenses to correspond with the classification of employees that receive stock option grants. No expense is recognized for any stock options ultimately forfeited because the recipients fail to meet vesting requirements. The Company also evaluates any subsequent changes to the respective option holders terms under the modification rules of ASC 718. If determined to be a modification, the Black-Scholes pricing model is updated as of the date of the modification resulting in a cumulative catch up to expense.
Income Taxes	Income Taxes —The provision for income taxes is calculated using the asset and liability method. Under the asset and liability method, deferred income taxes are recognized for the tax effect of temporary differences between the financial statement carrying amount of assets and liabilities and the amounts used for income tax purposes and for certain changes in valuation allowances. Valuation allowances are recorded to reduce certain deferred tax assets when, in our estimation, it is more likely than not that a tax benefit will not be realized.
Estimates	Estimates —The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Comprehensive Income (Loss)	Comprehensive Income (Loss) —The term “comprehensive income (loss)” represents the change in stockholders’ equity (deficit) from transactions and other events and circumstances resulting from non-stockholder sources. The Company’s accumulated other comprehensive income or loss, consisting principally of fair value adjustments to its interest rate swap and cap agreements (net of tax), cumulative foreign currency translation adjustments and pension liability adjustments (net of tax), is reported separately in the accompanying consolidated statements of comprehensive income.
Foreign Currency Transactions and Translations	Foreign Currency Translation and Transactions —The assets and liabilities of subsidiaries located outside the United States are translated into U.S. dollars at the rates of exchange in effect at the balance sheet dates. Revenue and expense items are translated at the average monthly exchange rates prevailing during the period. Gains and losses resulting from foreign currency transactions are recognized currently in income, and those resulting from translation of financial statements are accumulated as a separate component of other comprehensive income (loss) for the period. Foreign currency gains or losses recognized currently in income from changes in exchange rates were immaterial to our results of operations.
Earnings per Share	Earnings per Share —Earnings per share information is determined using the two-class method, which includes the weighted-average number of common shares outstanding during the period and other securities that participate in dividends (“participating securities”). Our vested stock options are considered “participating securities” because they include non-forfeitable rights to dividends. In applying the two-class method, earnings are allocated to both common stock shares and participating securities based on their respective weighted-average shares outstanding for the period. Diluted earnings per share information may include the additional effect of other securities, if dilutive, in which case the dilutive effect of such securities is calculated using the treasury stock method. Contingently issuable shares are not included in earnings per share until the period in which the contingency is satisfied; therefore, basic and diluted earnings per share are the same.
Pension and Other Postretirement Plans, Policy [Policy Text Block]	Pension Benefits —The Company accounts for pension expense using the end of the fiscal year as our measurement date. Management selects appropriate assumptions including the discount rate, rate of increase in future compensation levels and assumed long-term rate of return on plan assets. The assumptions are based upon historical results, the current economic environment and reasonable expectations of future events. Actual results which vary from our assumptions are accumulated and amortized over future periods, and accordingly, are recognized in expense in these periods. Significant differences between the assumptions and actual experience or significant changes in assumptions could impact the pension costs and the pension obligation.

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	12 Months Ended
	Sep. 30, 2020
Esterline [Member]
Business Acquisition [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	Assets acquired, excluding cash: Trade accounts receivable $ 384 Inventories 583 Prepaid expenses and other current assets 423 Property, plant, and equipment 469 Other intangible assets 1,301 Goodwill 2,256 Other 20 Total assets acquired, excluding cash 5,436 Liabilities assumed: Accounts payable 146 Other current liabilities 751 Other noncurrent liabilities 615 Total liabilities assumed 1,512 Net assets acquired $ 3,924

REVENUE RECOGNITION (Tables)

REVENUE RECOGNITION (Tables)	12 Months Ended
	Sep. 30, 2020
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, Initial Application Period Cumulative Effect Transition, Explanation of Change [Table Text Block]	September 30, 2020 September 30, 2019 Change Contract assets, current (1) $ 36 $ 44 $ (8) Contract assets, non-current (2) 6 7 (1) Total contract assets 42 51 (9) Contract liabilities, current (3) 18 18 — Contract liabilities, non-current (4) 9 13 (4) Total contract liabilities 27 31 (4) Net contract assets $ 15 $ 20 $ (5) (1) Included in prepaid expenses and other on the consolidated balance sheets. (2) Included in other non-current assets on the consolidated balance sheets. (3) Included in accrued liabilities on the consolidated balance sheets. (4) Included in other non-current liabilities on the consolidated balance sheets.

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Share	The following table sets forth the computation of basic and diluted earnings per share (in millions, except per share data) using the two-class method: Fiscal Years Ended September 30, 2020 2019 2018 Numerator for earnings per share: Income from continuing operations $ 653 $ 841 $ 962 Less: Net income attributable to noncontrolling interests (1) (2) — Net income from continuing operations attributable to TD Group 652 839 962 Less: Special dividends declared or paid on participating securities, including dividend equivalent payments (185) (111) (56) 467 728 906 Income (Loss) from discontinued operations, net of tax 47 51 (5) Net income applicable to TD Group common stockholders - basic and diluted $ 514 $ 779 $ 901 Denominator for basic and diluted earnings per share under the two-class method: Weighted-average common shares outstanding 53.9 53.1 52.3 Vested options deemed participating securities 3.4 3.2 3.3 Total shares for basic and diluted earnings per share 57.3 56.3 55.6 Earnings per share from continuing operations—basic and diluted $ 8.14 $ 12.94 $ 16.28 Earnings (Loss) per share from discontinued operations—basic and diluted 0.82 0.90 (0.08) Earnings per share $ 8.96 $ 13.84 $ 16.20

TRADE ACCOUNTS RECEIVABLE (Tabl

TRADE ACCOUNTS RECEIVABLE (Tables)	12 Months Ended
	Sep. 30, 2020
Receivables [Abstract]
Content Trade Accounts Receivable	Trade accounts receivable consist of the following (in millions): September 30, 2020 September 30, 2019 Trade accounts receivable—gross $ 757 $ 1,085 Allowance for uncollectible accounts (37) (17) Trade accounts receivable—net $ 720 $ 1,068

INVENTORIES (Tables)

INVENTORIES (Tables)	12 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Inventories	Inventories consist of the following (in millions): September 30, 2020 September 30, 2019 Raw materials and purchased component parts $ 881 $ 805 Work-in-progress 358 360 Finished goods 222 192 Total 1,461 1,357 Reserves for excess and obsolete inventory (178) (124) Inventories—Net $ 1,283 $ 1,233

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	12 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment consist of the following (in millions): September 30, 2020 September 30, 2019 Land and improvements $ 103 $ 96 Buildings and improvements 350 408 Machinery, equipment and other 782 628 Construction in progress 57 52 Total 1,292 1,184 Accumulated depreciation (540) (427) Property, plant and equipment—net $ 752 $ 757

INTANGIBLE ASSETS (Tables)

INTANGIBLE ASSETS (Tables)	12 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	Other intangible assets - net in the consolidated balance sheets consist of the following at September 30 (in millions): 2020 2019 Gross Carrying Accumulated Net Gross Carrying Accumulated Net Trademarks and trade names $ 958 $ — $ 958 $ 956 $ — $ 956 Technology 1,842 589 1,253 1,806 496 1,310 Order backlog 93 93 — 107 45 62 Customer relationships 443 52 391 438 30 408 Other 18 10 8 17 9 8 Total $ 3,354 $ 744 $ 2,610 $ 3,324 $ 580 $ 2,744
Schedule of Aggregate Amortization Expense	Information regarding the amortization expense of amortizable intangible assets is detailed below (in millions): Annual Amortization Expense: Fiscal years ended September 30, 2020 $ 169 2019 135 2018 72
Schedule of Finite-Lived Intangible Assets, Future Amortization	Estimated Amortization Expense: Fiscal years ending September 30, 2021 $ 115 2022 114 2023 114 2024 114 2025 114
Summary of Changes in Carrying Value of Goodwill	The changes in the carrying amount of goodwill by segment for the fiscal years ended September 30, 2019 and 2020 were as follows (in millions): Power & Airframe Non- Total Balance at September 30, 2018 $ 3,678 $ 2,452 $ 93 $ 6,223 Goodwill acquired during the year (Note 2) 469 1,180 546 2,195 Divestiture of goodwill acquired — — (43) (43) Reclass of goodwill acquired to assets held-for-sale (Note 23) — — (480) (480) Purchase price allocation adjustments (1) (9) (23) — (32) Currency translation adjustments (17) (11) (15) (43) Balance at September 30, 2019 4,121 3,598 101 7,820 Purchase price allocation adjustments (1) (1) 39 — 38 Currency translation adjustments 21 10 — 31 Balance at September 30, 2020 $ 4,141 $ 3,647 $ 101 $ 7,889

ACCRUED LIABILITIES (Tables)

ACCRUED LIABILITIES (Tables)	12 Months Ended
	Sep. 30, 2020
Payables and Accruals [Abstract]
Accrued Liabilities	Accrued liabilities consist of the following (in millions): September 30, 2020 September 30, 2019 Compensation and related benefits $ 173 $ 178 Interest 178 93 Interest rate swap agreements 56 13 Product warranties 32 34 Dividend equivalent payments—current (Note 18) 72 64 Environmental and other litigation reserves 15 12 Income taxes payable 19 44 Loss contract reserves 42 64 Other 186 173 Total $ 773 $ 675

DEBT (Tables)

DEBT (Tables)	12 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Schedule of Debt	The Company’s debt consists of the following (in millions): September 30, 2020 Gross Amount Debt Issuance Costs Original Issue Discount or Premium Net Amount Short-term borrowings—trade receivable securitization facility $ 350 $ (1) $ — $ 349 Term loans $ 7,449 $ (48) $ (23) $ 7,378 Revolving credit facility 200 — — 200 2024 Notes 1,200 (5) — 1,195 2025 Notes 750 (3) 3 750 2025 Secured Notes 1,100 (9) — 1,091 6.375% 2026 Notes 950 (6) — 944 6.875% 2026 Notes 500 (4) (3) 493 2026 Secured Notes 4,400 (55) 5 4,350 7.50% 2027 Notes 550 (5) — 545 5.50% 2027 Notes 2,650 (21) — 2,629 Government refundable advances 28 — — 28 Finance lease obligations 57 — — 57 19,834 (156) (18) 19,660 Less: current portion 277 (1) — 276 Long-term debt $ 19,557 $ (155) $ (18) $ 19,384 September 30, 2019 Gross Amount Debt Issuance Costs Original Issue Discount or Premium Net Amount Short-term borrowings—trade receivable securitization facility $ 350 $ — $ — $ 350 Term loans $ 7,524 $ (58) $ (17) $ 7,449 2022 Notes 1,150 (4) — 1,146 2024 Notes 1,200 (6) — 1,194 2025 Notes 750 (3) 3 750 6.375% 2026 Notes 950 (7) — 943 6.875% 2026 Notes 500 (6) (3) 491 2026 Secured Notes 4,000 (60) 2 3,942 7.50% 2027 Notes 550 (5) — 545 Government refundable advances 39 — — 39 Finance lease obligations 50 — — 50 16,713 (149) (15) 16,549 Less: current portion 81 (1) — 80 Long-term debt $ 16,632 $ (148) $ (15) $ 16,469
Schedule of Term Loans	As of September 30, 2020 and 2019, TransDigm had $7,449 million and $7,524 million in fully drawn term loans and $760 million in revolving commitments, of which $521 million and $719 million was available to the Company as of September 30, 2020 and 2019, respectively. The term loans consist of three tranches as follows (in millions): Term Loan Facility Maturity Date Interest Rate Aggregate Principal as of September 30, 2020 2019 Tranche E May 30, 2025 LIBOR + 2.25% $ 2,199 $ 2,221 Tranche F December 9, 2025 LIBOR + 2.25% $ 3,489 $ 3,524 Tranche G August 22, 2024 LIBOR + 2.25% $ 1,761 $ 1,779 The interest rates per annum applicable to all of the existing tranches of term loans are, at TransDigm’s option, equal to either an alternate base rate or an adjusted LIBOR for one, two, three or six-month (or to the extent agreed to by each relevant lender, nine or twelve-month) interest periods chosen by TransDigm, in each case plus an applicable margin percentage. The adjusted LIBOR is not subject to a floor. At September 30, 2020 and 2019, the applicable interest rates for all existing tranches were 2.41% and 4.83%, respectively.
Schedule of Subordinated Borrowing [Table Text Block]	Debt Repayment Schedule
Future Maturities of Long-Term Debt	At September 30, 2020, future maturities of long-term debt (includes finance leases) are as follows (in millions): Fiscal years ending September 30, 2021 $ 77 2022 81 2023 281 2024 2,970 2025 2,902 Thereafter 13,523 $ 19,834

RETIREMENT PLANS (Tables)

RETIREMENT PLANS (Tables)	12 Months Ended
	Sep. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions [Table Text Block]	U.S. Defined Benefit Pension Plans Non-U.S. Defined Benefit Pension Plans Principal assumptions as of year end: 2020 2019 2020 2019 Discount rate 2.47% 3.03% 1.90% 2.20% Rate of increase in future compensation levels 4.45% 4.48% 2.90% 2.98% Assumed long-term rate of return on plan assets 5.99% 6.00% 3.69% 4.16% U.S. Post-Retirement Pension Plans Non-U.S. Post Retirement Pension Plans Principal assumptions as of year end: 2020 2019 2020 2019 Discount rate 1.99% 2.86% 2.28% 2.68% Initial weighted average health care trend rate 7.27% 7.46% 5.50% 5.60% Ultimate weighted average health care trend rate 6.00% 6.00% 4.10% 4.10%
Defined Benefit Plan, Plan Assets, Allocation [Table Text Block]	Allocations by investment type are as follows : Actual Plan assets allocation as of fiscal year end: Target 2020 2019 Equity securities 35 - 70% 39.1% 35.1% Debt securities 30 - 65% 57.0% 59.5% Cash —% 3.9% 5.4% Total 100.0% 100.0%
Defined Benefit Plan, Plan Assets, Category [Table Text Block]	The following table presents the fair value of the Company’s pension plan assets as of September 30, 2020, by asset category segregated by level within the fair value hierarchy, as described in Note 20, “Fair Value Measurements” (in millions): Fair Value Hierarchy Level 1 Level 2 Total Investments measured at fair value by category: Equity Funds: (1) U.S. Equity Securities $ 4 $ — $ 4 Non-U.S. Equity Securities 48 — 48 Fixed Income Securities: (2) Non-U.S. Foreign Commercial and Government Bonds — 58 58 Cash and Cash Equivalents (3) 22 — 22 $ 74 $ 58 $ 132 Investments measured at net asset value by category: (4) Equity Funds: (1) Commingled Trust Funds - Non-U.S. Securities 153 Non-U.S. Equity Securities 9 Fixed Income Securities: (2) U.S. Government Bonds and Securities 80 U.S Corporate Bonds 123 Non-U.S. Corporate Bonds 18 Non-U.S. Foreign Commercial and Government Bonds 31 Total $ 546 The following table presents the fair value of the Company’s pension plan assets as of September 30, 2019, by asset category segregated by level within the fair value hierarchy, as described in Note 20, “Fair Value Measurements” (in millions): Fair Value Hierarchy Level 1 Level 2 Total Investments measured at fair value by category: Equity Funds: (1) U.S. Equity Securities $ 3 $ — $ 3 Non-U.S. Equity Securities 48 — 48 Fixed Income Securities: (2) Non-U.S. Foreign Commercial and Government Bonds — 86 86 Cash and Cash Equivalents (3) 30 — 30 $ 81 $ 86 $ 167 Investments measured at net asset value by category: (4) Equity Funds: (1) Commingled Trust Funds - Non-U.S. Securities 142 Fixed Income Securities: (2) U.S. Government Bonds and Securities 86 U.S Corporate Bonds 108 Non-U.S. Corporate Bonds 18 Non-U.S. Foreign Commercial and Government Bonds 30 Total $ 551 (1) Level 1 Equity Securities are actively traded on U.S. and non-U.S. exchanges and are either valued using the market approach at quoted market prices on the measurement date or at the net asset value of the shares held by the plan on the measurement date based on quoted market prices. (2) Level 2 Fixed Income Securities are primarily valued using the market approach at either quoted market prices, pricing models that use observable market data, or bids provided by independent investment brokerage firms. (3) Cash and Cash Equivalents include cash which is used to pay benefits and cash invested in a short-term investment fund that holds securities with values based on quoted market prices, but for which the funds are not valued on quoted market basis. (4) These investments are valued at the net asset value (“NAV”) of units held. The NAV is used to estimate fair value and is based on the fair value of the underlying investments held by the fund less its liability.
Schedule of Net Benefit Costs [Table Text Block]	Net periodic pension cost for the Company’s U.S. and non-U.S. defined benefit pension plans at the end of each fiscal year consisted of the following (in millions): Defined Benefit Pension Plans 2020 2019 2018 U.S. Pension Plans Non-U.S. Pension Plans U.S. Pension Plans Non-U.S. Pension Plans U.S. Pension Plans Non-U.S. Pension Plans Service cost $ 9 $ 6 $ 5 $ 3 $ 1 $ 1 Interest cost 10 5 7 5 1 2 Expected return on plan assets (19) (8) (10) (6) (1) (3) Amortization of actuarial loss (gain) 1 1 — — — 1 Curtailment/settlement loss (gain) (1) (1) — — — — Net periodic pension cost $ — $ 3 $ 2 $ 2 $ 1 $ 1
Schedule of Net Funded Status [Table Text Block]	The funded status of the defined benefit pension and post-retirement plans at the end of fiscal 2020 and 2019 were as follows (in millions): Defined Benefit Pension Plans Post-Retirement Pension Plans September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 U.S. Pension Plans Non-U.S. Pension Plans U.S. Pension Plans Non-U.S. Pension Plans U.S. Pension Plans Non-U.S. Pension Plans U.S. Pension Plans Non-U.S. Pension Plans Benefit Obligations Beginning balance $ 379 $ 270 $ 19 $ 73 $ 1 $ 14 $ 1 $ — Currency translation adjustment — 5 — (4) — — — — Service cost 9 6 5 3 — — — — Interest cost 10 5 8 5 — — — — Plan participant contributions — 1 — — — — — — Actuarial loss 10 13 43 28 — 1 — 1 Acquisitions — — 318 171 — — — 13 Curtailments — (2) — — — — — — Settlements (20) (40) — — — — — — Other adjustments — — — 1 — — — — Benefits paid (22) (10) (14) (7) — (1) — — Ending balance $ 366 $ 248 $ 379 $ 270 $ 1 $ 14 $ 1 $ 14 Plan Assets - Fair Value Beginning balance $ 318 $ 234 $ 9 $ 60 $ — $ — $ — $ — Currency translation adjustment — 3 — (3) — — — — Realized and unrealized gain on plan assets 44 8 31 19 — — — — Plan participants contributions — 1 — — — — — — Company contributions 21 8 2 3 — 1 — — Settlements (19) (40) — — — — — — Acquisitions — — 290 162 — — — — Other adjustments — — — — — — — — Expenses paid — — — — — — — — Benefits paid (22) (10) (14) (7) — (1) — — Ending balance $ 342 $ 204 $ 318 $ 234 $ — $ — $ — $ — Funded Status Fair value of plan assets $ 342 $ 204 $ 318 $ 234 $ — $ — $ — $ — Benefit obligations (366) (248) (379) (270) (1) (14) (1) (14) Net amount recognized $ (24) $ (44) $ (61) $ (36) $ (1) $ (14) $ (1) $ (14) Amount Recognized on Consolidated Balance Sheet Non-current asset $ — $ 4 $ — $ 4 $ — $ — $ — $ — Current liability (1) (1) (2) — — (1) — (1) Non-current liability (23) (47) (59) (40) (1) (13) (1) (13) Net amount recognized $ (24) $ (44) $ (61) $ (36) $ (1) $ (14) $ (1) $ (14) Amounts Recognized in Accumulated Other Comprehensive Income Net actuarial loss $ 12 $ 35 $ 28 $ 23 $ — $ 2 $ — $ 1 Prior service cost 1 1 1 1 — — — — Ending balance $ 13 $ 36 $ 29 $ 24 $ — $ 2 $ — $ 1
Schedule of Expected Benefit Payments [Table Text Block]	Estimated future benefit payments expected to be paid from the pension and post-retirement benefit plans or from the Company’s assets are as follows (in millions): Fiscal Year 2021 $ 31 2022 31 2023 32 2024 33 2025 34 2026 - 2030 182

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	The Company’s income from continuing operations before income taxes includes the following components for the periods shown below (in millions): Fiscal Years Ended September 30, 2020 2019 2018 United States $ 635 $ 878 $ 827 Foreign 105 185 159 $ 740 $ 1,063 $ 986
Income Tax Provision on Income Before Income Taxes	The Company’s income tax provision on income from continuing operations consists of the following for the periods shown below (in millions): Fiscal Years Ended September 30, 2020 2019 2018 Current Federal $ 26 $ 154 $ 137 State 3 15 12 Foreign 34 54 27 63 223 176 Deferred 24 (1) (152) $ 87 $ 222 $ 24
Schedule of Effective Income Tax Rate Reconciliation	The differences between the income tax provision on income from continuing operations at the federal statutory income tax rate and the tax provision shown in the accompanying consolidated statements of income for the periods shown below are as follows (in millions): Fiscal Years Ended September 30, 2020 2019 2018 Tax at statutory rate of 21% (21% for fiscal 2019 and 24.5% for fiscal 2018 ) $ 155 $ 223 $ 242 Stock compensation (79) (58) (51) Domestic manufacturing deduction — — (15) U.S. tax reform (1) — — (146) Foreign rate differential 5 2 (14) Foreign derived intangible income (20) (16) — Foreign tax credits (5) (18) (3) Changes in valuation allowances impacting results (2) 31 66 — Other—net — 23 11 Income tax provision $ 87 $ 222 $ 24
Components of Deferred Taxes	The components of the deferred taxes consist of the following at September 30 (in millions): 2020 2019 Deferred tax assets (liabilities): Intangible assets $ (730) $ (710) Property, plant and equipment (59) (64) Employee benefits 110 123 Interest rate swaps and caps 92 55 U.S. interest expense limitation 87 65 Loss contract reserves 55 63 Net operating losses 54 58 Inventories 41 39 Non-U.S. income tax credits 21 24 U.S. income tax credits 17 17 Environmental reserves 12 10 Product warranty reserves 10 8 Other 9 4 Total (281) (308) Add: Valuation allowance (132) (118) Total net deferred tax $ (413) $ (426)
Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in millions): 2020 2019 Balance at October 1 $ 37 $ 14 Additions based on tax positions related to the prior year 7 26 Additions based on tax positions related to the current year 2 — Reductions based on tax positions related to the prior year (1) (2) Settlement with tax authorities (2) — Lapse in statute of limitations (2) (1) Balance at September 30 $ 41 $ 37

SEGMENTS (Tables)

SEGMENTS (Tables)	12 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Net Sales by Reportable Segment	The following table presents net sales by reportable segment (in millions): Fiscal Years Ended September 30, 2020 2019 2018 Net sales to external customers Power & Control Commercial OEM $ 623 $ 686 $ 499 Commercial Aftermarket 673 769 665 Defense 1,399 1,281 975 Total Power & Control 2,695 2,736 2,139 Airframe Commercial OEM 783 836 509 Commercial Aftermarket 689 865 701 Defense 781 628 321 Total Airframe 2,253 2,329 1,531 Total Non-aviation 155 158 141 $ 5,103 $ 5,223 $ 3,811
EBITDA Defined by Segment to Consolidated Income Before Taxes Operations	The following table reconciles EBITDA As Defined by segment to consolidated income from continuing operations before income taxes (in millions): Fiscal Years Ended September 30, 2020 2019 2018 EBITDA As Defined Power & Control $ 1,345 $ 1,395 $ 1,115 Airframe 955 1,063 759 Non-aviation 54 51 44 Total segment EBITDA As Defined 2,354 2,509 1,918 Unallocated corporate expenses 76 90 41 Total Company EBITDA As Defined 2,278 2,419 1,877 Depreciation and amortization 283 225 129 Interest expense - net 1,029 859 663 Acquisition-related costs 31 169 29 Stock compensation expense 93 93 58 Refinancing costs 28 3 6 COVID-19 pandemic & 737 MAX restructuring costs 54 — — Other, net 20 7 6 Income from continuing operations before income taxes $ 740 $ 1,063 $ 986
Capital Expenditures and Depreciation and Amortization by Segment	The following table presents capital expenditures and depreciation and amortization by segment (in millions): Fiscal Years Ended September 30, 2020 2019 2018 Capital expenditures Power & Control $ 89 $ 50 $ 39 Airframe 10 48 32 Non-aviation 4 3 2 Corporate 2 1 — $ 105 $ 102 $ 73 Depreciation and amortization Power & Control $ 117 $ 99 $ 67 Airframe 157 119 56 Non-aviation 7 6 5 Corporate 2 2 1 $ 283 $ 226 $ 129
Total Assets by Segment	The following table presents total assets by segment (in millions): September 30, 2020 September 30, 2019 Total assets Power & Control $ 7,005 $ 7,037 Airframe 6,575 6,672 Non-aviation 251 262 Corporate 4,564 1,322 Assets of discontinued operations (Note 23) — 962 $ 18,395 $ 16,255

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Weighted Average Assumptions for all Options Granted Estimated at Grant Date Using Black-Scholes-Merton Option-Pricing Model	The fair value of the Company’s employee stock options was estimated at the date of grant or modification using a Black-Scholes option-pricing model with the following weighted average assumptions for all options granted during the fiscal years ended: Fiscal Years Ended September 30, 2020 2019 2018 Risk-free interest rate 0.26% to 1.65% 2.33% to 3.03% 2.01% to 2.84% Expected life of options 5 to 5.5 years 5.5 years 5.2 years Expected dividend yield of stock — — — Expected volatility of stock 25% to 39% 25% 25%
Summary of Activity, Pricing and Other Information for Performance Vested Stock-Based Award Activity	The following table summarizes the activity, pricing and other information for the Company’s performance vested stock-based award activity during the fiscal year ended September 30, 2020: Number of Weighted-Average Weighted-Average Aggregate Outstanding at September 30, 2019 3,167,458 $ 323.73 Granted 742,840 538.92 Exercised (34,495) 284.21 Forfeited (261,946) 372.81 Expired — — Outstanding at September 30, 2020 3,613,857 $ 364.79 7.6 years $ 398,716,843 Expected to vest 1,235,922 $ 332.98 7.5 years $ 175,676,981 Exercisable at September 30, 2020 1,709,551 $ 336.58 7.2 years $ 236,841,196 Number of Weighted-Average Weighted-Average Aggregate Outstanding at September 30, 2019 3,134,022 $ 155.34 Granted — — Exercised (887,842) 115.15 Forfeited (10,500) 226.34 Expired — — Outstanding at September 30, 2020 2,235,680 $ 170.97 3.4 years $ 679,982,072 Exercisable at September 30, 2020 2,235,680 $ 170.97 3.4 years $ 679,982,072

Leases, Codification Topic 840

Leases, Codification Topic 840 (Tables)	12 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Lease, Cost	The components of lease expense for the fiscal year ended September 30, 2020 are as follows (in millions): Classification Fiscal Year Ended September 30, 2020 Operating lease cost Cost of Sales or Selling and Administrative Expenses $ 29 Finance lease cost Amortization of leased assets Cost of Sales 3 Interest on lease liabilities Interest Expense - Net 4 Total lease cost $ 36
Schedule of Cash Flow, Supplemental Disclosures	Supplemental cash flow information related to leases for the fiscal year ended September 30, 2020 is as follows (in millions): Fiscal Year Ended September 30, 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash outflows from operating leases $ 29 Operating cash outflows from finance leases 4 Financing cash outflows from finance leases 2 Lease assets obtained in exchange for new lease obligations: Operating leases $ 32
Operating Leases, Supplemental Balance Sheet Information	Supplemental balance sheet information related to leases is as follows (in millions): Classification September 30, 2020 Operating Leases Operating lease right-of-use assets Other Assets $ 103 Current operating lease liabilities Accrued Liabilities 22 Long-term operating lease liabilities Other Non-current Liabilities 87 Total operating lease liabilities $ 109
Finance Leases, Supplemental Balance Sheet Information	Finance Leases Finance lease right-of-use assets, net Property, Plant and Equipment—Net $ 67 Current finance lease liabilities Accrued Liabilities 2 Long-term finance lease liabilities Other Non-current Liabilities 55 Total finance lease liabilities $ 57
Leases, Weighted-Average Term and Discount Rate Remaining	As of September 30, 2020, the Company has the following remaining lease term and weighted average discount rates: Weighted-average remaining lease term Operating leases 6.5 years Finance leases 16.4 years Weighted-average discount rate Operating leases 6.2% Finance leases 7.2%
Finance Lease, Liability, Maturity	Maturities of lease liabilities at September 30, 2020 are as follows (in millions): Operating Leases Finance Leases 2021 $ 28 $ 6 2022 24 6 2023 19 6 2024 16 6 2025 13 6 Thereafter 35 70 Total future minimum lease payments 135 100 Less: imputed interest 26 43 Present value of lease liabilities reported $ 109 $ 57
Lessee, Operating Lease, Liability, Maturity	Maturities of lease liabilities at September 30, 2020 are as follows (in millions): Operating Leases Finance Leases 2021 $ 28 $ 6 2022 24 6 2023 19 6 2024 16 6 2025 13 6 Thereafter 35 70 Total future minimum lease payments 135 100 Less: imputed interest 26 43 Present value of lease liabilities reported $ 109 $ 57

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Carrying Amounts and Fair Values of Financial Instruments	The following summarizes the carrying amounts and fair values of financial instruments (in millions): September 30, 2020 September 30, 2019 Level Carrying Fair Value Carrying Fair Value Assets: Cash and cash equivalents 1 $ 4,717 $ 4,717 $ 1,467 $ 1,467 Interest rate cap agreements (1) 2 — — 1 1 Liabilities: Interest rate swap agreements (2) 2 56 56 13 13 Interest rate swap agreements (3) 2 328 328 202 202 Foreign currency forward exchange contracts (3) 2 1 1 6 6 Short-term borrowings - trade receivable securitization facility (4) 1 349 349 350 350 Long-term debt, including current portion: Term loans (4) 2 7,378 7,004 7,449 7,478 Revolving credit facility (4) 2 200 200 — — 2022 Notes (4) 1 — — 1,146 1,167 2024 Notes (4) 1 1,195 1,194 1,194 1,239 2025 Notes (4) 1 750 743 750 782 2025 Secured Notes (4) 1 1,091 1,194 — — 6.375% 2026 Notes (4) 1 944 948 943 999 6.875% 2026 Notes (4) 1 493 500 491 535 6.25% 2026 Notes (4) 1 4,350 4,604 3,942 4,290 7.50% 2027 Notes (4) 1 545 569 545 595 5.50% 2027 Notes (4) 1 2,629 2,544 — — Government refundable advances 2 28 28 39 39 Finance lease obligations 2 57 57 50 50 (1) Included in other non-current assets on the consolidated balance sheets. (2) Included in accrued liabilities on the consolidated balance sheets. (3) Included in other non-current liabilities on the consolidated balance sheets. (4) The carrying amount of the debt instrument is presented net of the debt issuance costs, premium and discount. Refer to Note 12, “Debt,” for gross carrying amounts.

DERIVATIVES AND HEDGING ACTIV_2

DERIVATIVES AND HEDGING ACTIVITIES (Tables)	12 Months Ended
	Sep. 30, 2020
Derivative [Line Items]
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]	The following table summarizes the Company’s interest rate swap agreements: Aggregate Notional Amount Start Date End Date Related Term Loans Conversion of Related Variable Rate Debt to Fixed Rate of: $500 6/29/2018 3/31/2025 Tranche E 5.25% (3.0% plus the 2.25% margin percentage) $750 6/30/2020 6/30/2022 Tranche E 4.75% (2.5% plus the 2.25% margin percentage) $1,500 6/30/2022 3/31/2025 Tranche E 5.35% (3.1% plus the 2.25% margin percentage) $1,000 6/28/2019 12/9/2025 Tranche F 4.05% (1.8% plus the 2.25% margin percentage) $1,400 6/30/2021 12/9/2025 Tranche F 5.25% (3.0% plus the 2.25% margin percentage) $500 12/30/2016 12/31/2021 Tranche G 4.15% (1.9% plus the 2.25% margin percentage) $400 9/30/2017 9/30/2022 Tranche G 4.15% (1.9% plus the 2.25% margin percentage) $900 12/31/2021 6/28/2024 Tranche G 5.35% (3.1% plus the 2.25% margin percentage) $400 9/30/2022 6/28/2024 Tranche G 5.25% (3.0% plus the 2.25% margin percentage) The following table summarizes the Company’s interest rate cap agreements: Aggregate Notional Amount Start Date End Date Related Debt Offsets Variable Rate Debt Attributable to Fluctuations Above: $750 6/30/2020 6/30/2022 Tranche E Three month LIBOR of 2.5% $400 6/30/2016 6/30/2021 Tranche F Three month LIBOR of 2.0% $400 12/30/2016 12/31/2021 Tranche G Three month LIBOR of 2.5%
Schedule of Interest Rate Derivatives	September 30, 2020 September 30, 2019 Asset Liability Asset Liability Interest rate cap agreements $ — $ — $ 1 $ — Interest rate swap agreements (1) — (384) — (216) Net derivatives as classified in the balance sheet (2) $ — $ (384) $ 1 $ (216)

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	12 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	A summary of reclassifications out of accumulated other comprehensive (loss) income for the fiscal years ended September 30, 2020 and 2019 is provided below (in millions): Amount Reclassified Fiscal Years Ended September 30, Description of reclassifications out of accumulated other comprehensive (loss) income 2020 2019 Amortization from redesignated interest rate swap and cap agreements (1) $ 4 $ 3 Losses from settlement of foreign currency forward exchange contracts (2) (4) — Deferred tax expense on reclassifications out of accumulated other comprehensive (loss) income — 1 Losses reclassified into earnings, net of tax $ — $ 4 (1) This component of accumulated other comprehensive (loss) income is included in interest expense. Refer to Note 21, “Derivatives and Hedging Activities,” for additional information. (2) This component of accumulated other comprehensive (loss) income is included in net sales. Refer to Note 21, “Derivatives and Hedging Activities,” for additional information.
Schedule of Accumulated Other Comprehensive Loss	The following table presents the components of accumulated other comprehensive (loss) income, net of taxes, for the fiscal years ended September 30, 2020, 2019 and 2018 (in millions): Unrealized (loss) gain on derivatives designated and qualifying as cash flow hedges (1) Defined benefit pension plan activity (2) Currency translation adjustment Total Balance at September 30, 2018 $ 67 $ (11) $ (52) $ 4 Cumulative effect of ASU 2018-02, adopted October 1, 2018 (2) — — (2) Current-period other comprehensive loss (241) (29) (115) (385) Amounts reclassified from AOCI related to derivative instruments 4 — — 4 Net current-period other comprehensive loss (239) (29) (115) (383) Balance at September 30, 2019 (172) (40) (167) (379) Current-period other comprehensive (loss) gain (130) 32 76 (22) Balance at September 30, 2020 $ (302) $ (8) $ (91) $ (401) (1) Unrealized (loss) gain represents derivative instruments, net of taxes of $36, $70 and $(34) for the fiscal years ended September 30, 2020, 2019 and 2018, respectively. (1) Defined benefit pension plan and other post-retirement plan activity represents pension liability adjustments, net of taxes of $(1), $9 and $(1) for the fiscal years ended September 30, 2020, 2019 and 2018, respectively.

DISCONTINUED OPERATIONS (Tables

DISCONTINUED OPERATIONS (Tables)	12 Months Ended
	Sep. 30, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations [Table Text Block]	The table below summarizes income (loss) from discontinued operations, net of tax, for the fiscal years ended September 30, 2020, 2019 and 2018 (in millions): Fiscal Year Ended September 30, 2020 2019 2018 Net sales $ 79 $ 294 $ 12 Income (loss) from discontinued operations, before income taxes 11 — — Income tax provision (benefit) 4 (13) (2) Income from discontinued operations, net of tax 7 13 2 Gain (loss) from sale of discontinued operations, net of tax 40 38 (7) Income (loss) from discontinued operations, net of tax $ 47 $ 51 $ (5)
Souriau Sunbank [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations [Table Text Block]	The following is the summarized balance sheet of Souriau-Sunbank’s assets held-for-sale and liabilities held-for-sale as of September 30, 2019 (in millions): Assets and Liabilities of Discontinued Operations Held-for-Sale Fiscal Year Ended September 30, 2019 Cash and cash equivalents $ 29 Trade accounts receivable—Net 67 Inventories—Net 88 Prepaid expenses and other 2 Property, plant and equipment—Net 101 Goodwill 480 Other intangibles—Net 194 Other 1 Total assets of discontinued operations $ 962 Accounts payable $ 33 Accrued liabilities 55 Long-term debt 6 Deferred income taxes 42 Other 21 Total liabilities of discontinued operations $ 157

QUARTERLY FINANCIAL DATA (UNA_2

QUARTERLY FINANCIAL DATA (UNAUDTIED) (Tables)	12 Months Ended
	Sep. 30, 2020
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	First Quarter Second Quarter Third Quarter Fourth Quarter (in millions, except per share amounts) Fiscal Year Ended September 30, 2020 (1) Net sales (2) $ 1,465 $ 1,443 $ 1,022 $ 1,173 Gross profit (2) 801 818 491 536 Income (Loss) from continuing operations, net of tax (2) 234 323 (5) 101 Income (Loss) from discontinued operations, net of tax (2) 71 (4) (1) (19) Less: Net income attributable to noncontrolling interests (2) (1) — — — Net income (loss) attributable to TD Group (2) $ 304 $ 319 $ (6) $ 82 Net income (loss) attributable to TD Group common stockholders (3) $ 119 $ 319 $ (6) $ 82 Earnings (Loss) per share from continuing operations—basic and diluted (4) $ 0.83 $ 5.63 $ (0.09) $ 1.76 Earnings (Loss) per share from discontinued operations—basic and diluted (4) 1.24 (0.07) (0.01) (0.33) Earnings (Loss) per share (4) $ 2.07 $ 5.56 $ (0.10) $ 1.43 First Quarter Second Quarter Third Quarter Fourth Quarter (in millions, except per share amounts) Fiscal Year Ended September 30, 2019 (1) Net sales (2) $ 993 $ 1,168 $ 1,521 $ 1,541 Gross profit (2) 564 650 713 882 Income from continuing operations, net of tax (2) 196 200 128 317 Income from discontinued operations, net of tax (2) — 2 17 32 Less: Net income attributable to noncontrolling interests (2) — — — (2) Net income attributable to TD Group (2) $ 196 $ 202 $ 145 $ 347 Net income attributable to TD Group common stockholders (3) $ 172 $ 202 $ 145 $ 260 Earnings per share from continuing operations—basic and diluted (4) $ 3.05 $ 3.56 $ 2.27 $ 4.08 Earnings per share from discontinued operations—basic and diluted (4) — 0.04 0.30 0.55 Earnings per share (4) $ 3.05 $ 3.60 $ 2.57 $ 4.63 (1) Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Souriau-Sunbank and EIT at September 30, 2019, as discontinued operations. Refer to Note 23, “Discontinued Operations,” for additional information. (2) The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. Refer to Note 2 “Acquisitions and Divestitures,” for additional information. (3) Net income applicable to TD Group common stockholders represents net income attributable to TD Group less special dividends and dividend equivalent payments. Special dividend and dividend equivalent payments were $185 million, $24 million and $87 million, respectively, for the first quarter ended December 28, 2019, first quarter ended December 29, 2018 and fourth quarter ended September 30, 2019. (4) The sum of the earnings per share for the four quarters in a year does not necessarily equal the total year earnings per share due to the weighted average number of shares outstanding in each quarter.

DESCRIPTION OF THE BUSINESS A_2

DESCRIPTION OF THE BUSINESS AND IMPACT OF COVID-19 PANDEMIC - Narratives (Detail) $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)
Transdigm Inc [Member]
Accounting Policies [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Restructuring Cost and Reserve [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Minimum
Restructuring Cost and Reserve [Line Items]
Income Tax, Interest Disallowance Limitation	30.00%
Maximum
Restructuring Cost and Reserve [Line Items]
Income Tax, Interest Disallowance Limitation	50.00%
COVID-19 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	$ 46
Restructuring and Related Cost, Expected Cost Remaining	13
COVID-19 [Member] | Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	37
COVID-19 [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	$ 9

ACQUISITIONS - Narratives (Deta

ACQUISITIONS - Narratives (Detail) - USD ($) $ / shares in Units, $ in Millions	Dec. 20, 2019	Sep. 20, 2019	Aug. 30, 2019	Mar. 14, 2019	Oct. 01, 2018	Jul. 13, 2018	Apr. 24, 2018	Mar. 15, 2018	Jan. 26, 2018	Sep. 30, 2020		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Goodwill										$ 7,889		$ 7,889	$ 7,820	$ 6,223
Loss Contingency, Accrual, Current										42		42	64
Payments to Acquire Businesses, Net of Cash Acquired												0	3,976	668
NET SALES										1,173	[1],[2]	5,103	5,223	3,811
INCOME FROM CONTINUING OPERATIONS												653	841	962
AMORTIZATION OF INTANGIBLE ASSETS												169	135	72
Amortization of inventory step-up												0	77	7
Interest Income (Expense), Net												$ (1,029)	(859)	(663)
Minimum
Business Acquisition [Line Items]
Estimated useful life of aircraft (in years)												25 years
Maximum
Business Acquisition [Line Items]
Estimated useful life of aircraft (in years)												30 years
Esterline [Member]
Business Acquisition [Line Items]
Goodwill				$ 2,256
Loss Contingency Accrual				267.9						201.3		$ 201.3	231.8
Loss Contingency, Accrual, Current										31.9		31.9	60
Loss Contingency, Accrual, Noncurrent										$ 169.4		169.4	171.8
Loss Contingency Accrual, Period Increase (Decrease)												29.5	27.3
Amount of goodwill expected to be tax deductible				$ 25.6
Business Acquisition, Share Price				$ 122.50
Payments to Acquire Businesses, Net of Cash Acquired				$ 3,536.3
Business acquisition, assumption of net indebtedness				1,512
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents				398.2
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net				3,923.9
Restricted Cash, Current				387.6
Business acquisition, Intangibles, Tax Deductible Amount				48.9
Intangible assets				$ 1,301
Business Combination, Acquisition Related Costs												26.9	85.1
Souriau Sunbank [Member]
Business Acquisition [Line Items]
Loss Contingency Accrual													9.3
Skandia [Member]
Business Acquisition [Line Items]
Business Acquisition Purchase Price Adjustment														0.2
Payments to Acquire Businesses, Net of Cash Acquired						$ 84.3
Extant [Member]
Business Acquisition [Line Items]
Goodwill							$ 407
Tax benefit recognition period (in years)							15 years
Amount of goodwill expected to be tax deductible							$ 12.4
Business Acquisition Purchase Price Adjustment														0.2
Payments to Acquire Businesses, Net of Cash Acquired							533.1
Business acquisition, Intangibles, Tax Deductible Amount							62.5
Intangible assets							$ 105
Kirkhill [Member]
Business Acquisition [Line Items]
Business Acquisition Purchase Price Adjustment														0.6
Payments to Acquire Businesses, Net of Cash Acquired								$ 49.3
Stormscope [Member]
Business Acquisition [Line Items]
Tax benefit recognition period (in years)			15 years
Amount of goodwill expected to be tax deductible			$ 11.1
Payments to Acquire Businesses, Net of Cash Acquired			20
Business acquisition, Intangibles, Tax Deductible Amount			$ 7.5
NavCom [Member]
Business Acquisition [Line Items]
Tax benefit recognition period (in years)					15 years
Amount of goodwill expected to be tax deductible					$ 9
Payments to Acquire Businesses, Net of Cash Acquired					$ 27
Souriau Sunbank [Member]
Business Acquisition [Line Items]
Divestiture, Sale Price	$ 920
NET SALES												$ 79	$ 199
Divestiture, Working Capital Adjustment	$ 1.7
Esterline Interface Technology Group [Member]
Business Acquisition [Line Items]
Divestiture, Sale Price		$ 190
Divestiture, Working Capital Adjustment		$ 0.7												0.3
Schroth [Member]
Business Acquisition [Line Items]
Divestiture, Sale Price									$ 61.4
NET SALES														$ 12
[1]	Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Souriau-Sunbank and EIT at September 30, 2019, as discontinued operations. Refer to Note 23, “Discontinued Operations,” for additional information.
[2]	The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. Refer to Note 2 “Acquisitions and Divestitures,” for additional information. (3) Net income applicable to TD Group common stockholders represents net income attributable to TD Group less special dividends and dividend equivalent payments. Special dividend and dividend equivalent payments were $185 million, $24 million and $87 million, respectively, for the first quarter ended December 28, 2019, first quarter ended December 29, 2018 and fourth quarter ended September 30, 2019.

ACQUISITIONS - Schedule of Reco

ACQUISITIONS - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019	Mar. 14, 2019	Sep. 30, 2018	Apr. 24, 2018
Business Acquisition [Line Items]
Goodwill	$ 7,889	$ 7,820		$ 6,223
Esterline [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables			$ 384
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory			583
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets			423
Property, plant, and equipment			469
Intangible assets			1,301
Goodwill			2,256
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets			20
Total assets acquired			5,436
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable			146
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other			751
Other noncurrent liabilities			615
Total liabilities assumed			1,512
Net assets acquired			$ 3,923.9
Extant [Member]
Business Acquisition [Line Items]
Intangible assets					$ 105
Goodwill					$ 407

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narratives (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Summary Of Significant Accounting Policies [Line Items]
Research and development expense	$ 130.9	$ 116.8	$ 73.8
Land Improvements | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	10 years
Land Improvements | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	20 years
Building and improvements | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	5 years
Building and improvements | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	30 years
Machinery and equipment | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	2 years
Machinery and equipment | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	10 years
Furniture and Fixtures | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	3 years
Furniture and Fixtures | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	10 years
Technology Intangible Assets | Minimum
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	20 years
Technology Intangible Assets | Maximum
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	22 years
Order backlog | Minimum
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	1 year
Order backlog | Maximum
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	1 year 6 months
Other intangible assets | Minimum
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	20 years
Customer Relationships [Member] | Minimum
Summary Of Significant Accounting Policies [Line Items]
Finite lived intangible asset useful life	20 years

RECENT ACCOUNTING PRONOUNCEME_2

RECENT ACCOUNTING PRONOUNCEMENTS - Narratives (Details) - USD ($) $ in Millions	Sep. 30, 2020	Oct. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset		$ 99
Liabilities, Total [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Liability	$ 109
Other Non-Current Liabilities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Liability	$ 109	$ 105

REVENUE RECOGNITION (Details)

REVENUE RECOGNITION (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2020		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
NET SALES	$ 1,173	[1],[2]	$ 5,103	$ 5,223	$ 3,811
Contract with Customer, Asset, Net, Current	36		36	44
Contract with Customer, Asset, Current, Increase or Decrease			(8)
Contract with Customer, Asset, Net, Noncurrent	6		6	7
Contract with customer, Asset, Non-current, Increase or Decrease			(1)
Contract with Customer, Asset, after Allowance for Credit Loss	42		42	51
Contract assets, Increase or Decrease			(9)
Contract with Customer, Liability, Current	18		18	18
Contract liabilities, Current, Increase or Decrease			0
Contract with Customer, Liability, Noncurrent	9		9	13
Contract liabilities, Non-current, Increase or Decrease			(4)
Contract with Customer, Liability	27		27	31
Contract Liabilities, Increase or Decrease			(4)
Net Contract Asset	$ 15		15	$ 20
Net Contract Asset, Increase or Decrease			$ (5)
Revenue Benchmark [Member] | Customer 1
Percentage of net sales from one customer			10.00%	11.00%	11.00%
Revenue Benchmark [Member] | Customer 1 | Airframe
Percentage of net sales from one customer				60.00%
Revenue Benchmark [Member] | Customer 1 | Power & Control
Percentage of net sales from one customer				40.00%
Revenue Benchmark [Member] | Customer 2
Percentage of net sales from one customer					10.00%
Geographic Distribution, Foreign
NET SALES			$ 1,696	$ 1,778	$ 1,355
[1]	Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Souriau-Sunbank and EIT at September 30, 2019, as discontinued operations. Refer to Note 23, “Discontinued Operations,” for additional information.
[2]	The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. Refer to Note 2 “Acquisitions and Divestitures,” for additional information. (3) Net income applicable to TD Group common stockholders represents net income attributable to TD Group less special dividends and dividend equivalent payments. Special dividend and dividend equivalent payments were $185 million, $24 million and $87 million, respectively, for the first quarter ended December 28, 2019, first quarter ended December 29, 2018 and fourth quarter ended September 30, 2019.

EARNINGS PER SHARE - Computatio

EARNINGS PER SHARE - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2020		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
INCOME FROM CONTINUING OPERATIONS			$ 653	$ 841	$ 962
Less: Net income attributable to noncontrolling interests			(1)	(2)	0
Net income from continuing operations attributable to TD Group			652	839	962
Numerator for earnings per share:
Less: Special dividends declared or paid on participating securities, including dividend equivalent payments			(185)	(111)	(56)
Net Income Attributable to Continuing Operations Available To Common Stockholders Basic And Vested Options Deemed Participating Securities			467	728	906
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAX	$ (19)		47	51	(5)
Net income applicable to common stock-basic and diluted			$ 514	$ 779	$ 901
Denominator for basic and diluted earnings per share under the two-class method:
Weighted average common shares outstanding			53.9	53.1	52.3
Vested options deemed participating securities			3.4	3.2	3.3
Total shares for basic and diluted earnings per share (shares)			57.3	56.3	55.6
Earnings per share from continuing operations—basic and diluted	$ 1.76	[1],[2]	$ 8.14	$ 12.94	$ 16.28
Earnings (Loss) per share from discontinued operations—basic and diluted	$ (0.33)	[1],[2]	0.82	0.90	(0.08)
Earnings per share			$ 8.96	$ 13.84	$ 16.20
[1]	Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Souriau-Sunbank and EIT at September 30, 2019, as discontinued operations. Refer to Note 23, “Discontinued Operations,” for additional information.
[2]	The sum of the earnings per share for the four quarters in a year does not necessarily equal the total year earnings per share due to the weighted average number of shares outstanding in each quarter.

TRADE ACCOUNTS RECEIVABLE - Nar

TRADE ACCOUNTS RECEIVABLE - Narratives (Detail) - Accounts Receivable	12 Months Ended
	Sep. 30, 2020
Customer 1
Trade Accounts Receivable Securitization and Sale Program [Line Items]
Percentage of net sales from one customer	10.00%
Geographic Distribution, Foreign
Trade Accounts Receivable Securitization and Sale Program [Line Items]
Percentage of net sales from one customer	41.00%

TRADE ACCOUNTS RECEIVABLE - Con

TRADE ACCOUNTS RECEIVABLE - Content Trade Accounts Receivable (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Receivables [Abstract]
Trade accounts receivable—gross	$ 757	$ 1,085
Allowance for uncollectible accounts	(37)	(17)
Trade accounts receivable—net	$ 720	$ 1,068

INVENTORIES - Schedule of Inven

INVENTORIES - Schedule of Inventories (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Inventory Disclosure [Abstract]
Raw materials and purchased component parts	$ 881	$ 805
Work-in-progress	358	360
Finished goods	222	192
Total	1,461	1,357
Reserves for excess and obsolete inventory	(178)	(124)
Inventories—Net	$ 1,283	$ 1,233

PROPERTY, PLANT AND EQUIPMENT -

PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Land and improvements	$ 103	$ 96
Buildings and improvements	350	408
Machinery, equipment and other	782	628
Construction in progress	57	52
Total	1,292	1,184
Accumulated depreciation	(540)	(427)
Property, plant and equipment-net	$ 752	$ 757

INTANGIBLE ASSETS - Schedule of

INTANGIBLE ASSETS - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 3,354	$ 3,324
Intangible Assets, Accumulated Amortization	744	580
OTHER INTANGIBLE ASSETS—NET	2,610	2,744
Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,842	1,806
Accumulated Amortization	589	496
Net	1,253	1,310
Order backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	93	107
Accumulated Amortization	93	45
Net	0	62
Customer-Related Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	443	438
Accumulated Amortization	52	30
Net	391	408
Other intangible assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	18	17
Accumulated Amortization	10	9
Net	8	8
Trademarks and trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets (Excluding Goodwill), Gross	958	956
Indefinite-Lived Intangible Assets, Accumulated Amortization	0	0
Intangible Assets (Excluding Goodwill), Net	$ 958	$ 956

INTANGIBLE ASSETS - Schedule _2

INTANGIBLE ASSETS - Schedule of Aggregate Amortization Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 169	$ 135	$ 72

INTANGIBLE ASSETS - Schedule _3

INTANGIBLE ASSETS - Schedule of Finite-Lived Assets, Future Amortization (Details) $ in Millions	Sep. 30, 2020USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 115
Finite-Lived Intangible Assets, Amortization Expense, Year Two	114
Finite-Lived Intangible Assets, Amortization Expense, Year Three	114
Finite-Lived Intangible Assets, Amortization Expense, Year Four	114
Finite-Lived Intangible Assets, Amortization Expense, Year Five	$ 114

INTANGIBLE ASSETS - Schedule _4

INTANGIBLE ASSETS - Schedule of Intangible Assets Acquired (Detail) $ in Millions	12 Months Ended
	Sep. 30, 2019USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 2,195

INTANGIBLE ASSETS - Summary of

INTANGIBLE ASSETS - Summary of Changes in Carrying Value of Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 7,820	$ 6,223
Goodwill acquired during the year		2,195
Goodwill, Other Increase (Decrease)		(43)
Goodwill		(480)
Purchase price allocation adjustments	38	(32)
Goodwill, Foreign Currency Translation Gain (Loss)	31	(43)
Goodwill, Ending Balance	7,889	7,820
Souriau Sunbank [Member]
Goodwill [Line Items]
Goodwill		(480)
Power & Control
Goodwill [Line Items]
Goodwill, Beginning Balance	4,121	3,678
Goodwill acquired during the year		469
Goodwill, Other Increase (Decrease)		0
Goodwill		0
Purchase price allocation adjustments	(1)	(9)
Goodwill, Foreign Currency Translation Gain (Loss)	21	(17)
Goodwill, Ending Balance	4,141	4,121
Airframe
Goodwill [Line Items]
Goodwill, Beginning Balance	3,598	2,452
Goodwill acquired during the year		1,180
Goodwill, Other Increase (Decrease)		0
Goodwill		0
Purchase price allocation adjustments	39	(23)
Goodwill, Foreign Currency Translation Gain (Loss)	10	(11)
Goodwill, Ending Balance	3,647	3,598
Non-aviation
Goodwill [Line Items]
Goodwill, Beginning Balance	101	93
Goodwill acquired during the year		546
Goodwill, Other Increase (Decrease)		(43)
Goodwill		(480)
Purchase price allocation adjustments	0	0
Goodwill, Foreign Currency Translation Gain (Loss)	0	(15)
Goodwill, Ending Balance	$ 101	$ 101

ACCRUED LIABILITIES - Schedule

ACCRUED LIABILITIES - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Payables and Accruals [Abstract]
Compensation and related benefits	$ 173	$ 178
Interest	178	93
Interest rate swap agreements	56	13
Product warranties	32	34
Dividend Equivalent Payments On Certain Stock Options, Current	72.4	64
Environmental and other litigation reserves	15	12
Taxes Payable	19	44
Loss Contingency, Accrual, Current	42	64
Other	186	173
Total	$ 773	$ 675

DEBT - Narratives (Detail)

DEBT - Narratives (Detail) - USD ($) $ in Millions	Apr. 17, 2020	Apr. 08, 2020	Feb. 06, 2020	Oct. 29, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2014	Oct. 26, 2020	Mar. 24, 2020	Mar. 15, 2019	Feb. 01, 2019	May 08, 2018
Debt Instrument [Line Items]
Debt instrument, face amount					$ 19,834
Refinancing costs					$ 28	$ 3	$ 6
Debt Instrument, Interest Rate, Effective Percentage					1.85%
Long-term Debt, Gross					$ 19,834	16,713
Asset-backed Securities
Debt Instrument [Line Items]
Debt Instrument, Term								1 year
Short-term Bank Loans and Notes Payable, Gross					$ 350	350
Asset-backed Securities, Securitized Loans and Receivables [Member]
Debt Instrument [Line Items]
Basis spread on LIBOR					0.50%
Debt Instrument, Interest Rate, Stated Percentage					1.35%
Asset-backed Securities, Securitized Loans and Receivables [Member] | Asset-backed Securities
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable, Gross					$ 350
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity					760
Line of Credit Facility, Remaining Borrowing Capacity					$ 521	$ 719
Term Loans
Debt Instrument [Line Items]
Basis spread on LIBOR			2.25%
Debt Instrument, Interest Rate, Effective Percentage					2.41%	4.83%
Long-term Debt, Gross					$ 7,449	$ 7,524
Term Loans | Tranche G [Member]
Debt Instrument [Line Items]
Basis spread on LIBOR					2.25%		2.50%
Debt instrument, face amount			$ 1,774
Long-term Debt, Gross					$ 1,761	1,779
Term Loans | Tranche E
Debt Instrument [Line Items]
Basis spread on LIBOR					2.25%		2.50%
Debt instrument, face amount			2,216
Long-term Debt, Gross					$ 2,199	2,221
Term Loans | Tranche F
Debt Instrument [Line Items]
Debt Issuance Costs, Gross					$ 3.4
Basis spread on LIBOR					2.25%		2.50%
Debt instrument, face amount			3,515
Refinancing costs					$ 4.5
Long-term Debt, Gross					$ 3,489	$ 3,524
Debt Instrument, Unamortized Discount			$ 8.8
Senior Subordinated Notes | 5.50% Senior Subordinated Notes, Due 2020
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					5.50%	5.50%
Debt Instrument, Repurchased Face Amount											$ 550
Senior Subordinated Notes | 7.50% Senior Subordinated Notes, Due 2021
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					0.00%	7.50%
Senior Subordinated Notes | 6.00% Senior Subordinated Notes, Due 2022
Debt Instrument [Line Items]
Write-off of debt issuance costs					$ 3.8
Debt Instrument, Interest Rate, Stated Percentage				6.00%	6.00%	6.00%
Debt Instrument, Repurchased Face Amount				$ 1,150
Debt Instrument, Repurchase Amount				25.5
Long-term Debt, Gross						$ 1,150
Early Redemption Premium				$ 17.3
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2024
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					6.50%	6.50%
Long-term Debt, Gross					$ 1,200	$ 1,200
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2025
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					6.50%	6.50%
Long-term Debt, Gross					$ 750	$ 750
Senior Subordinated Notes | 6.375% Senior Subordinated Notes, Due 2026
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					6.375%	6.375%
Long-term Debt, Gross					$ 950	$ 950
Senior Subordinated Notes | Senior subordinated notes due 2026 6.875%
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					6.875%	0.00%
Long-term Debt, Gross					$ 500	$ 500							$ 500
Senior Subordinated Notes | Senior Subordinated Notes $550M Due 2027 7.50% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross					550	550
Senior Subordinated Notes | Senior Subordinated Notes $2650M Due 2027 5.50% [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Gross					23.8
Refinancing costs					1.1
Debt Instrument, Interest Rate, Stated Percentage				5.50%
Long-term Debt, Gross				$ 2,650	2,650
Senior Notes [Member] | Senior Secured Notes $4B Due 2026 6.25% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross						4,000						$ 4,000
Senior Notes [Member] | Senior Secured Notes $4.4B Due 2026 6.25% [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Gross					5.4
Debt Instrument, Interest Rate, Stated Percentage	6.25%
Long-term Debt, Gross					4,400
Senior Notes [Member] | Senior Secured Notes Due 2025 8.00%
Debt Instrument [Line Items]
Debt Issuance Costs, Gross					10.1
Debt Instrument, Redemption Price, Percentage		100.00%
Debt Instrument, Interest Rate, Stated Percentage		8.00%
Long-term Debt, Gross		$ 1,100			1,100
Senior Notes [Member] | Senior Secured Notes $400M due 2026 6.25% [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	101.00%
Debt Instrument, Interest Rate, Stated Percentage	6.25%
Long-term Debt, Gross	$ 400
Government Refundable Advances [Member]
Debt Instrument [Line Items]
Government refundable advances					28.4	39.2
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital Lease Obligations					$ 56.8	$ 49.9
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Basis spread on LIBOR					0.75%
Debt Instrument, Interest Rate, Stated Percentage					3.00%
Debt Instrument, Interest Rate, Effective Percentage					3.75%
Letters of Credit Outstanding, Amount					$ 39.4
Line of Credit Facility, Remaining Borrowing Capacity					520.6
Long-term Debt, Gross					$ 200					$ 200
Subsequent Event [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross									$ 200

DEBT - Schedule of Debt (Detail

DEBT - Schedule of Debt (Detail) - USD ($) $ in Millions	Apr. 08, 2020	Sep. 30, 2020	Apr. 17, 2020	Mar. 24, 2020	Oct. 29, 2019	Sep. 30, 2019	Feb. 01, 2019	May 08, 2018
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage		1.85%
Debt Issuance Costs, Net		$ (156)				$ (149)
Debt Instrument, Unamortized Discount (Premium), Net		18				15
Short-term borrowings—trade receivable securitization facility		349				350
Long-term Debt, Gross		19,834				16,713
Total debt outstanding		19,660				16,549
Less current portion		276				80
Long-term Debt, Excluding Current Maturities, Gross		19,557				16,632
Deferred Finance Costs, Excluding Current Maturities		(155)				(148)
Debt Instrument, Unamortized Discount, Excluding Current Maturities		(18)				(15)
Long-term debt		$ 19,384				$ 16,469
Term Loans
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage		2.41%				4.83%
Debt Issuance Costs, Net		$ (48)				$ (58)
Debt Instrument, Unamortized Discount (Premium), Net		23				17
Long-term Debt, Gross		7,449				7,524
Total debt outstanding		7,378				7,449
Government Refundable Advances [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Net		0				0
Debt Instrument, Unamortized Discount (Premium), Net		0				0
Total debt outstanding		28				39
Government refundable advances		28.4				39.2
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Net		0				0
Debt Instrument, Unamortized Discount (Premium), Net		0				0
Total debt outstanding		57				50
Capital Lease Obligations		$ 56.8				49.9
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage		3.75%
Debt Issuance Costs, Net		$ 0
Debt Instrument, Unamortized Discount (Premium), Net		0
Long-term Debt, Gross		$ 200		$ 200
Debt Instrument, Interest Rate, Stated Percentage		3.00%
Total debt outstanding		$ 200				0
Long-term Debt, Current Maturities
Debt Instrument [Line Items]
Debt Issuance Costs, Net		(1)				(1)
Debt Instrument, Unamortized Discount (Premium), Net		0				0
Long-term Debt, Current Maturities, Gross		277				81
Less current portion		276				80
Asset-backed Securities
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable, Gross		350				350
Debt Issuance Costs, Net		(1)				0
Debt Instrument, Unamortized Discount (Premium), Net		0				0
Short-term borrowings—trade receivable securitization facility		$ 349				$ 350
Asset-backed Securities, Securitized Loans and Receivables [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.35%
Asset-backed Securities, Securitized Loans and Receivables [Member] | Asset-backed Securities
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable, Gross		$ 350
5.50% Senior Subordinated Notes, Due 2020 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.50%				5.50%
7.50% Senior Subordinated Notes, Due 2021 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		0.00%				7.50%
6.00% Senior Subordinated Notes, Due 2022 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net						$ (4)
Debt Instrument, Unamortized Discount (Premium), Net						0
Long-term Debt, Gross						$ 1,150
Debt Instrument, Interest Rate, Stated Percentage		6.00%			6.00%	6.00%
Total debt outstanding		$ 0				$ 1,146
6.50% Senior Subordinated Notes, Due 2024 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net		(5)				(6)
Debt Instrument, Unamortized Discount (Premium), Net		0				0
Long-term Debt, Gross		$ 1,200				$ 1,200
Debt Instrument, Interest Rate, Stated Percentage		6.50%				6.50%
Total debt outstanding		$ 1,195				$ 1,194
6.50% Senior Subordinated Notes, Due 2025 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net		(3)				(3)
Debt Instrument, Unamortized Discount (Premium), Net		(3)				(3)
Long-term Debt, Gross		$ 750				$ 750
Debt Instrument, Interest Rate, Stated Percentage		6.50%				6.50%
Total debt outstanding		$ 750				$ 750
6.375% Senior Subordinated Notes, Due 2026 | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net		(6)				(7)
Debt Instrument, Unamortized Discount (Premium), Net		0				0
Long-term Debt, Gross		$ 950				$ 950
Debt Instrument, Interest Rate, Stated Percentage		6.375%				6.375%
Total debt outstanding		$ 944				$ 943
Senior subordinated notes due 2026 6.875% | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net		(4)				(6)
Debt Instrument, Unamortized Discount (Premium), Net		3				3
Long-term Debt, Gross		$ 500				$ 500		$ 500
Debt Instrument, Interest Rate, Stated Percentage		6.875%				0.00%
Total debt outstanding		$ 493				$ 491
Senior Secured Notes $4B Due 2026 6.25% [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Net						(60)
Debt Instrument, Unamortized Discount (Premium), Net						(2)
Long-term Debt, Gross						4,000	$ 4,000
Total debt outstanding						3,942
Senior Subordinated Notes $550M Due 2027 7.50% [Member] | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net		(5)				(5)
Debt Instrument, Unamortized Discount (Premium), Net		0				0
Long-term Debt, Gross		550				550
Total debt outstanding		545				545
Senior Secured Notes Due 2025 8.00% | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Net		(9)
Debt Instrument, Unamortized Discount (Premium), Net		0
Long-term Debt, Gross	$ 1,100	1,100
Debt Instrument, Interest Rate, Stated Percentage	8.00%
Total debt outstanding		1,091				0
Debt Instrument, Redemption Price, Percentage	100.00%
Senior Secured Notes $4.4B Due 2026 6.25% [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Net		(55)
Debt Instrument, Unamortized Discount (Premium), Net		(5)
Long-term Debt, Gross		4,400
Debt Instrument, Interest Rate, Stated Percentage			6.25%
Total debt outstanding		4,350
Senior Subordinated Notes $2650M Due 2027 5.50% [Member] | Senior Subordinated Notes
Debt Instrument [Line Items]
Debt Issuance Costs, Net		(21)
Debt Instrument, Unamortized Discount (Premium), Net		0
Long-term Debt, Gross		2,650			$ 2,650
Debt Instrument, Interest Rate, Stated Percentage					5.50%
Total debt outstanding		$ 2,629				$ 0

DEBT - Schedule of Term Loans (

DEBT - Schedule of Term Loans (Details) - USD ($) $ in Millions	Feb. 06, 2020	Sep. 30, 2020	Sep. 30, 2018	Oct. 29, 2019	Sep. 30, 2019
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 19,834			$ 16,713
Term Loans
Debt Instrument [Line Items]
Basis spread on LIBOR	2.25%
Long-term Debt, Gross		$ 7,449			7,524
Term Loans | Tranche E
Debt Instrument [Line Items]
Basis spread on LIBOR		2.25%	2.50%
Long-term Debt, Gross		$ 2,199			2,221
Term Loans | Tranche F
Debt Instrument [Line Items]
Basis spread on LIBOR		2.25%	2.50%
Long-term Debt, Gross		$ 3,489			3,524
Term Loans | Tranche G [Member]
Debt Instrument [Line Items]
Basis spread on LIBOR		2.25%	2.50%
Long-term Debt, Gross		$ 1,761			$ 1,779
Senior Subordinated Notes | 5.50% Senior Subordinated Notes, Due 2020
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.50%			5.50%
Senior Subordinated Notes | 7.50% Senior Subordinated Notes, Due 2021
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		0.00%			7.50%
Senior Subordinated Notes | 6.00% Senior Subordinated Notes, Due 2022
Debt Instrument [Line Items]
Long-term Debt, Gross					$ 1,150
Debt Instrument, Interest Rate, Stated Percentage		6.00%		6.00%	6.00%
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2024
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 1,200			$ 1,200
Debt Instrument, Interest Rate, Stated Percentage		6.50%			6.50%
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2025
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 750			$ 750
Debt Instrument, Interest Rate, Stated Percentage		6.50%			6.50%
Senior Subordinated Notes | 6.375% Senior Subordinated Notes, Due 2026
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 950			$ 950
Debt Instrument, Interest Rate, Stated Percentage		6.375%			6.375%

DEBT - Future Maturities of Lon

DEBT - Future Maturities of Long-Term Debt (Detail) $ in Millions	Sep. 30, 2020USD ($)
Debt Disclosure [Abstract]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 77
Long-term Debt, Maturities, Repayments of Principal in Year Two	81
Long-term Debt, Maturities, Repayments of Principal in Year Three	281
Long-term Debt, Maturities, Repayments of Principal in Year Four	2,970
Long-term Debt, Maturities, Repayments of Principal in Year Five	2,902
Long-term Debt, Maturities, Repayments of Principal after Year Five	13,523
Debt Instrument, Face Amount	$ 19,834

DEBT -Schedule of Subordinated

DEBT -Schedule of Subordinated Borrowings (Details) - USD ($) $ in Millions	Sep. 30, 2020	Oct. 29, 2019	Sep. 30, 2019	May 08, 2018
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 19,834		$ 16,713
Senior Subordinated Notes | 5.50% Senior Subordinated Notes, Due 2020
Subordinated Borrowing [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.50%		5.50%
Senior Subordinated Notes | 6.00% Senior Subordinated Notes, Due 2022
Subordinated Borrowing [Line Items]
Long-term Debt, Gross			$ 1,150
Debt Instrument, Interest Rate, Stated Percentage	6.00%	6.00%	6.00%
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2024
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 1,200		$ 1,200
Debt Instrument, Interest Rate, Stated Percentage	6.50%		6.50%
Senior Subordinated Notes | 6.50% Senior Subordinated Notes, Due 2025
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 750		$ 750
Debt Instrument, Interest Rate, Stated Percentage	6.50%		6.50%
Senior Subordinated Notes | 6.375% Senior Subordinated Notes, Due 2026
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 950		$ 950
Debt Instrument, Interest Rate, Stated Percentage	6.375%		6.375%
Senior Subordinated Notes | Senior subordinated notes due 2026 6.875%
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 500		$ 500	$ 500
Debt Instrument, Interest Rate, Stated Percentage	6.875%		0.00%
Senior Subordinated Notes | Senior Subordinated Notes $550M Due 2027 7.50% [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 550		$ 550

RETIREMENT PLANS - Narratives (

RETIREMENT PLANS - Narratives (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Mar. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Discount rate decrease by 25 basis points, change in pension obligation		$ 20.3
Discount rate increase by 25 basis points, change in pension obligation		17.1
Change in Net Periodic Benefit Cost, if 25 basis point decrease in discount rate		0.1
Increase in expected return on assets by 25 basis points, change in net periodic benefit cost		1.3
Decrease in expected return on assets by 25 basis points, change in net periodic benefit costs		1.3
Defined contribution plan, cost recognized	$ 14.9	25.3	$ 24.5
Defined benefit plan, accumulated benefit obligation		595.3	623.8
Change in Net Periodic Benefit Cost, if 25 basis point increase in discount rate		$ 0.2
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate		5.50%
Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		$ 1.7	1.4
Unqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		19.8	0.9
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		1
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		342	318	$ 9
Defined benefit plan, accumulated benefit obligation		358.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	1	0	2
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation		366.2
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(24)	(61)
Defined Benefit Plan, Plan Assets, Contributions by Employer		21	2
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		20	0
Defined Benefit Plan, Benefit Obligation, Decrease for Settlements		19.4
Defined Benefit Plan, Unfunded Status of Plan		(24.2)
UNITED STATES | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		0.9
UNITED STATES | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0	0	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(1)	(1)
Defined Benefit Plan, Plan Assets, Contributions by Employer		0	0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		0	0
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		3.1
Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		204.3	234	60
Defined benefit plan, accumulated benefit obligation		237.2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 1	3	2
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation		247.8
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(44)	(36)
Defined Benefit Plan, Plan Assets, Contributions by Employer		8.3	2.7
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		40.1	0
Defined Benefit Plan, Unfunded Status of Plan		(47.5)
Foreign Plan [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0	0	$ 0
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(14)	(14)
Defined Benefit Plan, Plan Assets, Contributions by Employer		1	0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		$ 0	$ 0

RETIREMENT PLANS Tables (Detail

RETIREMENT PLANS Tables (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Mar. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage		100.00%	100.00%
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months		$ 31
Defined Benefit Plan, Expected Future Benefit Payment, Year Two		31
Defined Benefit Plan, Expected Future Benefit Payment, Year Three		32
Defined Benefit Plan, Expected Future Benefit Payment, Year Four		33
Defined Benefit Plan, Expected Future Benefit Payment, Year Five		34
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter		182
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		74	$ 81
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		$ 58	$ 86
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage		39.10%	35.10%
Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		$ 4	$ 3
Defined Benefit Plan, Equity Securities, US [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		4	3
Defined Benefit Plan, Equity Securities, US [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0	0
Defined Benefit Plan, Equity Securities, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		48	48
Defined Benefit Plan, Equity Securities, Non-US [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		48	48
Defined Benefit Plan, Equity Securities, Non-US [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0	0
Defined Benefit Plan, Equity Securities, Non-US [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		9
US Treasury and Government [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		80	86
Defined Benefit Plan, Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		22	30
Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		22	30
Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0	0
Debt Security, Corporate, US [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		123	108
Debt Security, Corporate, Non-US [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		18	18
Debt Security, Government, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		58	86
Debt Security, Government, Non-US [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0	0
Debt Security, Government, Non-US [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		58	86
Debt Security, Government, Non-US [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		$ 31	$ 30
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage		57.00%	59.50%
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage		3.90%	5.40%
Defined Benefit Plan, Commingled Equity Securities, Non-US | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		$ 153	$ 142
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer		3.1
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		$ 1
Other Postretirement Benefits Plan [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		1.99%	2.86%
Defined Benefit Plan, Benefit Obligation		$ 1	$ 1	$ 1
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)		0	0
Defined Benefit Plan, Service Cost		0	0
Defined Benefit Plan, Interest Cost		0	0
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant		0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		0	0
Defined Benefit Plan, Benefit Obligation, Business Combination		0	0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment		0	0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change		0	0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		0	0
Defined Benefit Plan, Benefit Obligation, Benefits Paid		0	0
Defined Benefit Plan, Plan Assets, Amount		0	0	0
Defined Benefit Plan, Benefit Obligations		(1)	(1)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)		0	0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)		0	0
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant		0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer		0	0
Defined Benefit Plan, Plan Assets, Payment for Settlement		0	0
Defined Benefit Plan, Plan Assets, Business Combination		0	0
Defined benefit plan, Plan assets, Other change		0	0
Defined Benefit Plan, Plan Assets, Administration Expense		0	0
Defined Benefit Plan, Plan Assets, Benefits Paid		0	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(1)	(1)
Assets for Plan Benefits, Defined Benefit Plan		0	0
Liability, Defined Benefit Plan, Current		0	0
Liability, Defined Benefit Plan, Noncurrent		(1)	(1)
Liability, Defined Benefit Plan		(1)	(1)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax		0	0
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax		0	0
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax		$ 0	$ 0
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year		7.27%	7.46%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate		6.00%	6.00%
Other Postretirement Benefits Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		2.28%	2.68%
Defined Benefit Plan, Benefit Obligation		$ 14	$ 14	0
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)		0	0
Defined Benefit Plan, Service Cost		0	0
Defined Benefit Plan, Interest Cost		0	0
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant		0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		1	1
Defined Benefit Plan, Benefit Obligation, Business Combination		0	13
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment		0	0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change		0	0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		0	0
Defined Benefit Plan, Benefit Obligation, Benefits Paid		(1)	0
Defined Benefit Plan, Plan Assets, Amount		0	0	0
Defined Benefit Plan, Benefit Obligations		(14)	(14)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)		0	0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)		0	0
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant		0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer		1	0
Defined Benefit Plan, Plan Assets, Payment for Settlement		0	0
Defined Benefit Plan, Plan Assets, Business Combination		0	0
Defined benefit plan, Plan assets, Other change		0	0
Defined Benefit Plan, Plan Assets, Administration Expense		0	0
Defined Benefit Plan, Plan Assets, Benefits Paid		(1)	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(14)	(14)
Assets for Plan Benefits, Defined Benefit Plan		0	0
Liability, Defined Benefit Plan, Current		(1)	(1)
Liability, Defined Benefit Plan, Noncurrent		(13)	(13)
Liability, Defined Benefit Plan		(14)	(14)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax		2	1
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax		0	0
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax		$ 2	$ 1
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year		5.50%	5.60%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate		4.10%	4.10%
Pension Plan [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		2.47%	3.03%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase		4.45%	4.48%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		5.99%	6.00%
Defined Benefit Plan, Benefit Obligation		$ 366	$ 379	19
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)		0	0
Defined Benefit Plan, Service Cost	$ 1	9	5
Defined Benefit Plan, Interest Cost	1	10	8
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant		0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		10	43
Defined Benefit Plan, Benefit Obligation, Business Combination		0	318
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment		0	0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change		0	0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		(20)	0
Defined Benefit Plan, Benefit Obligation, Benefits Paid		(22)	(14)
Defined Benefit Plan, Plan Assets, Amount		342	318	9
Defined Benefit Plan, Benefit Obligations		(366)	(379)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)		0	0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)		44	31
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant		0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer		21	2
Defined Benefit Plan, Plan Assets, Payment for Settlement		(19)	0
Defined Benefit Plan, Plan Assets, Business Combination		0	290
Defined benefit plan, Plan assets, Other change		0	0
Defined Benefit Plan, Plan Assets, Administration Expense		0	0
Defined Benefit Plan, Plan Assets, Benefits Paid		(22)	(14)
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(24)	(61)
Assets for Plan Benefits, Defined Benefit Plan		0	0
Liability, Defined Benefit Plan, Current		(1)	(2)
Liability, Defined Benefit Plan, Noncurrent		(23)	(59)
Liability, Defined Benefit Plan		(24)	(61)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax		12	28
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax		1	1
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax		13	29
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(1)	(19)
Defined Benefit Plan, Amortization of Gain (Loss)	0	1
Defined Benefit Plan, Benefit Obligation, Payment for Settlement		(1)	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	1	$ 0	$ 2
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		1.90%	2.20%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase		2.90%	2.98%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		3.69%	4.16%
Defined Benefit Plan, Benefit Obligation		$ 248	$ 270	73
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)		5	(4)
Defined Benefit Plan, Service Cost	1	6	3
Defined Benefit Plan, Interest Cost	2	5	5
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant		1	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		13	28
Defined Benefit Plan, Benefit Obligation, Business Combination		0	171
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment		(2)	0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Other Change		0	1
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		(40.1)	0
Defined Benefit Plan, Benefit Obligation, Benefits Paid		(10)	(7)
Defined Benefit Plan, Plan Assets, Amount		204.3	234	60
Defined Benefit Plan, Benefit Obligations		(248)	(270)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)		3	(3)
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)		8	19
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant		1	0
Defined Benefit Plan, Plan Assets, Contributions by Employer		8.3	2.7
Defined Benefit Plan, Plan Assets, Payment for Settlement		(40)	0
Defined Benefit Plan, Plan Assets, Business Combination		0	162
Defined benefit plan, Plan assets, Other change		0	0
Defined Benefit Plan, Plan Assets, Administration Expense		0	0
Defined Benefit Plan, Plan Assets, Benefits Paid		(10)	(7)
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(44)	(36)
Assets for Plan Benefits, Defined Benefit Plan		4	4
Liability, Defined Benefit Plan, Current		(1)	0
Liability, Defined Benefit Plan, Noncurrent		(47)	(40)
Liability, Defined Benefit Plan		(44)	(36)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax		35	23
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax		1	1
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax		36	24
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(3)	(8)
Defined Benefit Plan, Amortization of Gain (Loss)	1	1
Defined Benefit Plan, Benefit Obligation, Payment for Settlement		(1)	0	$ 0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 1	3	2
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		546	551
Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		$ 132	$ 167

INCOME TAXES - Narratives (Deta

INCOME TAXES - Narratives (Detail) - USD ($) $ in Millions	Jan. 01, 2018	Mar. 31, 2018	Mar. 30, 2019	Sep. 30, 2020	Sep. 30, 2018	Sep. 30, 2019
Income Tax Contingency [Line Items]
Statutory tax rate		35.00%	35.00%	21.00%	24.50%
State tax credit carryforward				$ 38.2
State tax credit carryforward expiration period				2025
Effect of unrecognized tax benefits on effective tax rate				$ 40.9		$ 36.7
Accrual for income tax penalties and interest				8.7		$ 5
Decrease in Unrecognized Tax Benefits is Reasonably Possible				20
U.S. Tax Cuts and Jobs Act Effective 2018 [Member]
Income Tax Contingency [Line Items]
Statutory tax rate	21.00%
Deferred Federal Income Tax Expense (Benefit)				176.4
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount				30
State
Income Tax Contingency [Line Items]
Net operating loss carryforward				$ 1,482.1
Minimum
Income Tax Contingency [Line Items]
Net tax loss carryforwards, expiration years				2020
Maximum
Income Tax Contingency [Line Items]
Net tax loss carryforwards, expiration years				2039
UNITED KINGDOM | Federal and United Kingdom
Income Tax Contingency [Line Items]
Net operating loss carryforward				$ 12.3
GERMANY | Federal and United Kingdom
Income Tax Contingency [Line Items]
Net operating loss carryforward				18.1
BELGIUM | Federal and United Kingdom
Income Tax Contingency [Line Items]
Net operating loss carryforward				$ 47

INCOME TAXES - Income Tax Provi

INCOME TAXES - Income Tax Provision on Income Before Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Current
Federal	$ 26	$ 154	$ 137
State	3	15	12
Foreign	34	54	27
Total Current	63	223	176
Deferred	24	(1)	(152)
Income tax provision	$ 87	$ 222	$ 24

INCOME TAXES - Income Tax Expen

INCOME TAXES - Income Tax Expense Reconciliation (Detail) - USD ($) $ in Millions		3 Months Ended	6 Months Ended	12 Months Ended
		Mar. 31, 2018	Mar. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Tax at statutory rate of 35%				$ 155	$ 223	$ 242
Income Tax Effects Allocated Directly to Equity, Employee Stock Options				(79)	(58)	(51)
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount				5	2	(14)
Effective income tax rate reconciliation, foreign derived intangible income, amount				(20)	(16)	0
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount				31	66	0
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount				5	18	3
Domestic manufacturing deduction				0	0	(15)
Effective Income Tax Reconciliation, Deduction for US Tax Reform Act	[1]			0	0	146
Other-net				0	(23)	(11)
Income tax provision				$ 87	$ 222	$ 24
Statutory tax rate		35.00%	35.00%	21.00%		24.50%
[1]	On December 22, 2017, the Tax Cuts and Jobs Act (the “Act”) was enacted. The Act reduces the U.S. federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings from certain foreign subsidiaries that were previously deferred as well as other changes. We recorded tax benefits of $176.4 million related to the remeasurement of our net U.S. deferred tax liabilities to reflect the reduction in the corporate tax rate. We also recorded tax expense of $30.0 million related to the one-time transition tax.

INCOME TAXES - Components of De

INCOME TAXES - Components of Deferred Taxes (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Intangible assets	$ (730)	$ (710)
Property, plant and equipment	(59)	(64)
Interest rate swaps	92	55
Employee benefits, compensation and other accrued obligations	110	123
Deferred Tax Liabilities, U.S. Interest Expense Limitation	87	65
Deferred Income Tax Liability, Loss Contract Reserve	55	63
Net operating losses	54	58
Inventory	41	39
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	21	24
Deferred Tax Assets, Tax Credit Carryforwards	17	17
Environmental	12	10
Product warranties	10	8
Other	9	4
Total deferred tax liabilities	(281)	(308)
Add: Valuation allowance	(132)	(118)
Total net deferred tax liabilities	$ (413)	$ (426)

INCOME TAXES - Reconciliation o

INCOME TAXES - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 37	$ 14
Additions based on tax positions related to the prior year	7	26
Additions based on tax positions related to the current year	2	0
Reductions based on tax positions related to the prior year	(1)	(2)
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	2	0
Lapse in statute of limitations	(2)	(1)
Balance at end of period	$ 41	$ 37

INCOME TAXES Income before Tax

INCOME TAXES Income before Tax from Continuing Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income before Tax from Continuing Operations [Abstract]
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ 635	$ 878	$ 827
Income (Loss) from Continuing Operations before Income Taxes, Foreign	105	185	159
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	$ 740	$ 1,063	$ 986

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Accrued Environmental Loss Contingencies, Current	$ 7.9	$ 9.4
Accrued Environmental Loss Contingencies, Noncurrent	43.1	$ 32.7
Insurance deductible	1
Fire Related Expense	17
Unusual or Infrequent Item, or Both, Insurance Proceeds	$ 27

CAPITAL STOCK - Narratives (Det

CAPITAL STOCK - Narratives (Detail) - USD ($) $ / shares in Units, $ in Millions	Mar. 28, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Nov. 08, 2017
Shareholders Equity [Line Items]
Common stock, shares authorized		224,400,000	224,400,000
Common stock, par value		$ 0.01	$ 0.01
Preferred stock, shares authorized		149,600,000
Preferred stock, par value		$ 0.01
Common stock, shares issued		58,612,028	57,623,311
Treasury stock, shares		4,198,226	4,161,326
Preferred stock, shares outstanding		0
Stock Repurchased and Retired During Period, Shares	36,900
Payments for Repurchase of Common Stock		$ 19	$ 0	$ 0
Non-cash stock compensation		92.7	$ 93.4	$ 58.5
November 8, 2017 Stock Repurchase Program [Member]
Shareholders Equity [Line Items]
Stock Repurchase Program, Authorized Amount		650			$ 650
Payments for Repurchase of Common Stock	$ 18.9
Treasury Stock Acquired, Average Cost Per Share	$ 512.67
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 631.1

SEGMENTS - Narratives (Detail)

SEGMENTS - Narratives (Detail)	12 Months Ended
	Sep. 30, 2020Segment
Segment Reporting [Abstract]
Number of reporting segments	3

SEGMENTS - Net Sales by Reporta

SEGMENTS - Net Sales by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2020	[1],[2]	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
NET SALES	$ 1,173		$ 5,103	$ 5,223	$ 3,811
Operating Segments | Power & Control
Segment Reporting Information [Line Items]
NET SALES			2,695	2,736	2,139
Operating Segments | Airframe
Segment Reporting Information [Line Items]
NET SALES			2,253	2,329	1,531
Operating Segments | Non-aviation
Segment Reporting Information [Line Items]
NET SALES			155	158	141
Commercial OEM [Member] | Operating Segments | Power & Control
Segment Reporting Information [Line Items]
NET SALES			623	686	499
Commercial OEM [Member] | Operating Segments | Airframe
Segment Reporting Information [Line Items]
NET SALES			783	836	509
Commercial Aftermarket [Member] | Operating Segments | Power & Control
Segment Reporting Information [Line Items]
NET SALES			673	769	665
Commercial Aftermarket [Member] | Operating Segments | Airframe
Segment Reporting Information [Line Items]
NET SALES			689	865	701
Defense [Member] | Operating Segments | Power & Control
Segment Reporting Information [Line Items]
NET SALES			1,399	1,281	975
Defense [Member] | Operating Segments | Airframe
Segment Reporting Information [Line Items]
NET SALES			$ 781	$ 628	$ 321
[1]	Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Souriau-Sunbank and EIT at September 30, 2019, as discontinued operations. Refer to Note 23, “Discontinued Operations,” for additional information.
[2]	The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. Refer to Note 2 “Acquisitions and Divestitures,” for additional information. (3) Net income applicable to TD Group common stockholders represents net income attributable to TD Group less special dividends and dividend equivalent payments. Special dividend and dividend equivalent payments were $185 million, $24 million and $87 million, respectively, for the first quarter ended December 28, 2019, first quarter ended December 29, 2018 and fourth quarter ended September 30, 2019.

SEGMENTS - EBITDA Defined by Se

SEGMENTS - EBITDA Defined by Segment to Consolidated Income Before Taxes Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	$ 2,278	$ 2,419	$ 1,877
Depreciation and amortization	283	226	129
Interest Income (Expense), Net	(1,029)	(859)	(663)
Stock compensation expense	92.7	93.4	58.5
Refinancing costs	28	3	6
Income before income taxes	740	1,063	986
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	2,354	2,509	1,918
Operating Segments | Power & Control
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	1,345	1,395	1,115
Depreciation and amortization	117	99	67
Operating Segments | Airframe
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	955	1,063	759
Depreciation and amortization	157	119	56
Operating Segments | Non-aviation
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	54	51	44
Depreciation and amortization	7	6	5
Corporate, Non-Segment [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Earnings before interest taxes depreciation and amortization	76	90	41
Depreciation and amortization	2	2	1
Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Depreciation and amortization	283	225	129
Interest Income (Expense), Net	1,029	859	663
Acquisition-related costs	31	169	29
Stock compensation expense	93	93	58
Refinancing costs	28	3	6
COVID-19 & 737 MAX restructuring costs	54	0	0
Other nonrecurring charges	$ 20	$ 7	$ 6

SEGMENTS - Capital Expenditures

SEGMENTS - Capital Expenditures and Depreciation and Amortization by Segment (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Capital expenditures	$ 105	$ 102	$ 73
Depreciation and amortization	283	226	129
Operating Segments | Power & Control
Segment Reporting Information [Line Items]
Capital expenditures	89	50	39
Depreciation and amortization	117	99	67
Operating Segments | Airframe
Segment Reporting Information [Line Items]
Capital expenditures	10	48	32
Depreciation and amortization	157	119	56
Operating Segments | Non-aviation
Segment Reporting Information [Line Items]
Capital expenditures	4	3	2
Depreciation and amortization	7	6	5
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Capital expenditures	2	1	0
Depreciation and amortization	$ 2	$ 2	$ 1

SEGMENTS - Total Assets by Segm

SEGMENTS - Total Assets by Segment (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 18,395	$ 16,255
Operating Segments | Power & Control
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	7,005	7,037
Operating Segments | Airframe
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	6,575	6,672
Operating Segments | Non-aviation
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	251	262
Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	4,564	1,322
Discontinued Operations, Held-for-sale [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 0	$ 962

STOCK-BASED COMPENSATION - Narr

STOCK-BASED COMPENSATION - Narratives (Detail) - USD ($)	1 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2011	Mar. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Oct. 03, 2019	Oct. 02, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash stock compensation			$ 92,700,000	$ 93,400,000	$ 58,500,000
Stock option weighted-average grant date fair value		$ 81.04	$ 157.41	$ 114.43
Unrecognized compensation cost related to non-vested awards expected to vest			$ 62,800,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition			1 year 8 months 12 days
Share-based Payment Arrangement, Plan Modification, Incremental Cost			$ 2,500,000
Fair value of options vested			$ 97,200,000	$ 37,700,000	44,400,000
Restricted stock outstanding			0
Cash dividend and dividend equivalents paid			$ 74,000,000	80,000,000	17,000,000
Payments of Dividends			1,928,000,000	1,712,000,000	56,000,000
Dividend Equivalent Payments On Certain Stock Options, Current			72,400,000	64,000,000
Dividend Equivalent Payments on Certain Stock Options, Non-current			49,000,000
2019 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock						4,000,000
2014 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock							5,000,000
2006 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock	8,119,668
Restricted stock grant period in years	3 years
2003 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total intrinsic value of options exercised			$ 394,200,000	240,200,000	192,500,000
2014 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for award			1,316,998
Vested Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend, Share-based Payment Arrangement, Cash			$ 184,900,000	$ 111,000,000	$ 56,100,000
Performance Vested Stock Options | 2014 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for award			742,840
Number of Options, Exercised			34,495
Weighted-Average Exercise Price Per Option, Exercised			$ 284.21
Number of Options Exercisable at end of period			1,709,551
Weighted-Average Exercise Price Per Option, Exercisable			$ 336.58
Weighted-Average Remaining Contractual Term, Exercisable, years			7 years 2 months 12 days
Aggregate Intrinsic Value, Exercisable			$ 236,841,196
Performance Vested Stock Options | 2006 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for award			0
Number of Options, Exercised			887,842
Weighted-Average Exercise Price Per Option, Exercised			$ 115.15
Number of Options Exercisable at end of period			2,235,680
Weighted-Average Exercise Price Per Option, Exercisable			$ 170.97
Weighted-Average Remaining Contractual Term, Exercisable, years			3 years 4 months 24 days
Aggregate Intrinsic Value, Exercisable			$ 679,982,072
Performance Vested Stock Options | 2003 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options Exercisable at end of period			829	77,829
Weighted-Average Exercise Price Per Option, Exercisable			$ 130.09
Weighted-Average Remaining Contractual Term, Exercisable, years			2 years 1 month 6 days
Aggregate Intrinsic Value, Exercisable			$ 300,000

STOCK-BASED COMPENSATION - Weig

STOCK-BASED COMPENSATION - Weighted Average Assumptions used to Estimate Fair Value of all Options at Grant Date using Black-Scholes-Merton Option-Pricing Model (Detail)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement [Abstract]
Risk-free interest rate, minimum	0.26%	2.33%	2.01%
Risk-free interest rate, maximum	1.65%	3.03%	2.84%
Expected dividend yield of stock	0.00%	0.00%	0.00%
Expected volatility of stock		25.00%	25.00%
Expected life of options		5 years 6 months	5 years 2 months 12 days
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	0.26%	2.33%	2.01%
Risk-free interest rate, maximum	1.65%	3.03%	2.84%
Expected life of options		5 years 6 months	5 years 2 months 12 days
Expected volatility of stock		25.00%	25.00%
Minimum
Share-based Payment Arrangement [Abstract]
Expected volatility of stock	25.00%
Expected life of options	5 years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options	5 years
Expected volatility of stock	25.00%
Maximum
Share-based Payment Arrangement [Abstract]
Expected volatility of stock	39.00%
Expected life of options	5 years 6 months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options	5 years 6 months
Expected volatility of stock	39.00%

STOCK-BASED COMPENSATION - Summ

STOCK-BASED COMPENSATION - Summary of Activity, Pricing and Other Information for Performance Vested Stock-Based Award Activity (Detail) - Performance Vested Stock Options - USD ($)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
2014 Stock Option Plan
Number of Options
Number of Options, Outstanding, beginning of period	3,167,458
Number of Options, Granted	742,840
Number of Options, Exercised	(34,495)
Number of Options, Forfeited	(261,946)
Number of Options, Expired	0
Number of Options, Outstanding, end of period	3,613,857	3,167,458
Number of Options, Expected to vest	1,235,922
Number of Options Exercisable at end of period	1,709,551
Weighted average exercise price per option
Weighted-Average Exercise Price Per Option, Outstanding, beginning of period	$ 323.73
Weighted-Average Exercise Price Per Option, Granted	538.92
Weighted-Average Exercise Price Per Option, Exercised	284.21
Weighted-Average Exercise Price Per Option, Forfeited	372.81
Weighted-Average Exercise Price Per Option, Expired	0
Weighted-Average Exercise Price Per Option, Outstanding, end of period	364.79	$ 323.73
Weighted-Average Exercise Price Per Option, Expected to vest	332.98
Weighted-Average Exercise Price Per Option, Exercisable	$ 336.58
Weighted average remaining contractual term
Weighted-Average Remaining Contractual Term, Outstanding, years	7 years 7 months 6 days
Weighted-Average Remaining Contractual Term, Expected to vest, years	7 years 6 months
Weighted-Average Remaining Contractual Term, Exercisable, years	7 years 2 months 12 days
Aggregate intrinsic value
Aggregate Intrinsic Value, Outstanding	$ 398,716,843
Aggregate Intrinsic Value, Expected to vest	175,676,981
Aggregate Intrinsic Value, Exercisable	$ 236,841,196
2006 Stock Incentive Plan
Number of Options
Number of Options, Outstanding, beginning of period	3,134,022
Number of Options, Granted	0
Number of Options, Exercised	(887,842)
Number of Options, Forfeited	(10,500)
Number of Options, Expired	0
Number of Options, Outstanding, end of period	2,235,680	3,134,022
Number of Options Exercisable at end of period	2,235,680
Weighted average exercise price per option
Weighted-Average Exercise Price Per Option, Outstanding, beginning of period	$ 155.34
Weighted-Average Exercise Price Per Option, Granted	0
Weighted-Average Exercise Price Per Option, Exercised	115.15
Weighted-Average Exercise Price Per Option, Forfeited	226.34
Weighted-Average Exercise Price Per Option, Expired	0
Weighted-Average Exercise Price Per Option, Outstanding, end of period	170.97	$ 155.34
Weighted-Average Exercise Price Per Option, Exercisable	$ 170.97
Weighted average remaining contractual term
Weighted-Average Remaining Contractual Term, Outstanding, years	3 years 4 months 24 days
Weighted-Average Remaining Contractual Term, Exercisable, years	3 years 4 months 24 days
Aggregate intrinsic value
Aggregate Intrinsic Value, Outstanding	$ (679,982,072)
Aggregate Intrinsic Value, Exercisable	$ 679,982,072
2003 Stock Option Plan
Number of Options
Number of Options Exercisable at end of period	829	77,829
Weighted average exercise price per option
Weighted-Average Exercise Price Per Option, Exercisable	$ 130.09
Weighted average remaining contractual term
Weighted-Average Remaining Contractual Term, Exercisable, years	2 years 1 month 6 days
Aggregate intrinsic value
Aggregate Intrinsic Value, Exercisable	$ 300,000

LEASES - Components of Lease Ex

LEASES - Components of Lease Expense (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)
Leases [Abstract]
Operating Lease, Cost	$ 29
Finance Lease, Right-of-Use Asset, Amortization	3
Finance Lease, Interest Expense	4
Lease, Cost	$ 36

LEASES - Supplemental Cash Flow

LEASES - Supplemental Cash Flow Information Related to Leases (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020USD ($)
Leases [Abstract]
Operating Lease, Payments	$ 29
Finance Lease, Principal Payments	4
Finance Lease, Interest Payment on Liability	2
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 32

LEASES - Operating Leases, Supp

LEASES - Operating Leases, Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Sep. 30, 2020	Oct. 01, 2019
Operating Leased Assets [Line Items]
Operating Lease, Right-of-Use Asset		$ 99
Other Assets [Member]
Operating Leased Assets [Line Items]
Operating Lease, Right-of-Use Asset	$ 103
Accrued Liabilities
Operating Leased Assets [Line Items]
Operating Lease, Liability, Current	22
Other Non-Current Liabilities
Operating Leased Assets [Line Items]
Operating Lease, Liability, Noncurrent	87
Operating Lease, Liability	109	$ 105
Liabilities, Total [Member]
Operating Leased Assets [Line Items]
Operating Lease, Liability	$ 109

LEASES - Finance Leases, Supple

LEASES - Finance Leases, Supplemental Balance Sheet Information (Details) $ in Millions	Sep. 30, 2020USD ($)
Capital Leased Assets [Line Items]
Finance Lease, Right-of-Use Asset	$ 67
Finance Lease, Liability, Current	2
Finance Lease, Liability, Noncurrent	55
Finance Lease, Liability	$ 57

LEASES - Weighted-Average Term

LEASES - Weighted-Average Term and Discount Rate Remaining (Details)	Sep. 30, 2020
Leases [Abstract]
Operating Lease, Weighted Average Remaining Lease Term	6 years 6 months
Finance Lease, Weighted Average Remaining Lease Term	16 years 4 months 24 days
Operating Lease, Weighted Average Discount Rate, Percent	6.20%
Finance Lease, Weighted Average Discount Rate, Percent	7.20%

LEASES - Maturities of Lease Li

LEASES - Maturities of Lease Liabilities Operating and Financing (Details) $ in Millions	Sep. 30, 2020USD ($)
Leases [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	$ 28
Lessee, Operating Lease, Liability, Payments, Due Year Two	24
Lessee, Operating Lease, Liability, Payments, Due Year Three	19
Lessee, Operating Lease, Liability, Payments, Due Year Four	16
Lessee, Operating Lease, Liability, Payments, Due Year Five	13
Lessee, Operating Lease, Liability, Payments, Due after Year Five	35
Lessee, Operating Lease, Liability, Payments, Due	135
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	26
Finance Lease, Liability, Payments, Due Next Twelve Months	6
Finance Lease, Liability, Payments, Due Year Two	6
Finance Lease, Liability, Payments, Due Year Three	6
Finance Lease, Liability, Payments, Due Year Four	6
Finance Lease, Liability, Payments, Due Year Five	6
Finance Lease, Liability, Payments, Due after Year Five	70
Finance Lease, Liability, Payment, Due	100
Finance Lease, Liability, Undiscounted Excess Amount	43
Finance Lease, Liability	$ 57

LEASES - Narratives (Details)

LEASES - Narratives (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Operating Leases, Rent Expense, Net	$ 26	$ 19
Operating Leases, Future Minimum Payments Due, Next Twelve Months	22
Operating Leases, Future Minimum Payments, Due in Two Years	32
Operating Leases, Future Minimum Payments, Due in Three Years	17
Operating Leases, Future Minimum Payments, Due in Four Years	14
Operating Leases, Future Minimum Payments, Due in Five Years	13
Operating Leases, Future Minimum Payments, Due Thereafter	$ 28

FAIR VALUE MEASUREMENTS Carryin

FAIR VALUE MEASUREMENTS Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, Assets, Carrying Amount	$ 4,717	$ 1,467
Short-term borrowings - trade receivable securitization facility, Carrying Amount	349	350
Long-term Debt	19,660	16,549
Other Noncurrent Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Cash Flow Hedge Asset at Carrying Value	0	1
Accrued Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements, Liabilities, Carrying Amount	56	13
Foreign Currency Contract, Asset	1	6
Other Non-Current Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements, Liabilities, Carrying Amount	328	202
Term Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	7,378	7,449
Revolving Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	200	0
Government Refundable Advances [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	28	39
Capital Lease Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	57	50
Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, Assets, Fair Value	4,717	1,467
Fair Value, Inputs, Level 2 [Member] | Other Noncurrent Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	0	1
Fair Value, Inputs, Level 2 [Member] | Accrued Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Cash Flow Hedge Liability at Fair Value	56	13
Foreign Currency Contract, Asset	1	6
Fair Value, Inputs, Level 2 [Member] | Other Non-Current Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Cash Flow Hedge Liability at Fair Value	328	202
Fair Value, Inputs, Level 2 [Member] | Term Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	7,004	7,478
Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	200	0
Fair Value, Inputs, Level 2 [Member] | Government Refundable Advances [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	28	39
Fair Value, Inputs, Level 2 [Member] | Capital Lease Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	57	50
6.00% Senior Subordinated Notes, Due 2022 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	0	1,146
6.00% Senior Subordinated Notes, Due 2022 | Fair Value, Inputs, Level 1 [Member] | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	0	1,167
6.50% Senior Subordinated Notes, Due 2024 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	1,195	1,194
6.50% Senior Subordinated Notes, Due 2024 | Fair Value, Inputs, Level 1 [Member] | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	1,194	1,239
6.50% Senior Subordinated Notes, Due 2025 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	750	750
6.50% Senior Subordinated Notes, Due 2025 | Fair Value, Inputs, Level 1 [Member] | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	743	782
Senior Secured Notes Due 2025 8.00% | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	1,091	0
Senior Secured Notes Due 2025 8.00% | Fair Value, Inputs, Level 1 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	1,194	0
6.375% Senior Subordinated Notes, Due 2026 | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	944	943
6.375% Senior Subordinated Notes, Due 2026 | Fair Value, Inputs, Level 1 [Member] | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	948	999
Senior subordinated notes due 2026 6.875% | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	493	491
Senior subordinated notes due 2026 6.875% | Fair Value, Inputs, Level 1 [Member] | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	500	535
Senior Secured Notes $4.4B Due 2026 6.25% [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	4,350
Senior Secured Notes $4.4B Due 2026 6.25% [Member] | Fair Value, Inputs, Level 1 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	4,604
Senior Secured Notes $4B Due 2026 6.25% [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt		3,942
Senior Secured Notes $4B Due 2026 6.25% [Member] | Fair Value, Inputs, Level 1 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value		4,290
Senior Subordinated Notes $550M Due 2027 7.50% [Member] | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	545	545
Long-term debt, Fair Value		595
Senior Subordinated Notes $550M Due 2027 7.50% [Member] | Fair Value, Inputs, Level 1 [Member] | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	569
Senior Subordinated Notes $2650M Due 2027 5.50% [Member] | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	2,629	0
Senior Subordinated Notes $2650M Due 2027 5.50% [Member] | Fair Value, Inputs, Level 1 [Member] | Senior Subordinated Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	2,544	0
Asset-backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings - trade receivable securitization facility, Carrying Amount	349	350
Asset-backed Securities | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings - trade receivable securitization facility, Fair Value	$ 349	$ 350

DERIVATIVES AND HEDGING ACTIV_3

DERIVATIVES AND HEDGING ACTIVITIES - Narratives (Detail) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Interest Rate Swap and Cap
Derivative [Line Items]
Derivative loss to be recognized		$ 10.3
interest expense, derivative instruments settlements		2.2
Foreign Exchange Forward [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Gross Amount to be Transferred		1.2
Derivative, Notional Amount		172.5
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Interest Expense	[1]	$ (4)	$ (3)
Tranche F | Interest Rate Cap
Derivative [Line Items]
Derivative, Cap Interest Rate		2.50%
Tranche F | Interest rate cap agreements beginning June 30, 2016
Derivative [Line Items]
Derivative, Cap Interest Rate		2.00%
Derivative, Notional Amount		$ 400
Tranche F | Interest rate swap June 28, 2016 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		4.30%
Tranche F | Interest rate swap beginning June 30, 2021 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.50%
Derivative, Notional Amount		$ 1,400
Tranche F | Interest rate swap June 28, 2019 [Member]
Derivative [Line Items]
Derivative, Notional Amount		1,000
Tranche E | Interest rate cap beginning September 30, 2015
Derivative [Line Items]
Derivative, Notional Amount		$ 750
Tranche E | Interest rate swap beginning June 30, 2020 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.00%
Derivative, Notional Amount		$ 750
Tranche E | Interest rate swap beginning March 31, 2016 [Member]
Derivative [Line Items]
Derivative, Notional Amount		750
Tranche G [Member] | Interest Rate Cap
Derivative [Line Items]
Derivative, Notional Amount		$ 400
Tranche G [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		4.40%
Derivative, Notional Amount		$ 500
Tranche G [Member] | Interest rate swap beginning September 30, 2017 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		4.40%
Derivative, Notional Amount		$ 400
Tranche G [Member] | Interest rate swap beginning December 31, 2021 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.60%
Derivative, Notional Amount		$ 900
Tranche G [Member] | Interest rate swap beginning September 30, 2022 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.50%
Derivative, Notional Amount		$ 400
Sales [Member]
Derivative [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net		3.9
Selling, General and Administrative Expenses [Member]
Derivative [Line Items]
Gain (Loss) on foreign currency contracts not designated as accounting hedges		0.7
Other Nonoperating Income (Expense) [Member]
Derivative [Line Items]
Gain (Loss) on Foreign Currency Fair Value Hedge Derivatives		$ 1.6
[1]	This component of accumulated other comprehensive (loss) income is included in interest expense. Refer to Note 21, “Derivatives and Hedging Activities,” for additional information.

DERIVATIVES AND HEDGING ACTIV_4

DERIVATIVES AND HEDGING ACTIVITIES - Schedule of Interest Rate Derivatives (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Sep. 30, 2019
Derivative [Line Items]
Derivative Asset	[1]	$ 0	$ 1,000
Derivative Liability	[1]	(384,000)	(216,000)
Interest Rate Cap
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	1,000
Derivative Asset, Fair Value, Gross Liability		0	0
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	[2]	0	0
Derivative Asset, Fair Value, Gross Liability	[2]	$ (384,000)	$ (216,000)
Tranche F | Interest rate swap beginning June 30, 2021 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.50%
Derivative, Variable Interest Rate		3.00%
Derivative, Basis Spread on Variable Rate		2.50%
Tranche F | Interest Rate Cap
Derivative [Line Items]
Derivative, Cap Interest Rate		2.50%
Tranche F | Interest rate cap agreements beginning June 30, 2016
Derivative [Line Items]
Derivative, Cap Interest Rate		2.00%
Tranche F | Interest rate swap June 28, 2016 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		4.30%
Derivative, Variable Interest Rate		1.80%
Derivative, Basis Spread on Variable Rate		2.50%
Tranche G [Member] | Interest rate swap beginning September 30, 2017 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		4.40%
Derivative, Variable Interest Rate		1.90%
Derivative, Basis Spread on Variable Rate		2.50%
Tranche G [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		4.40%
Derivative, Variable Interest Rate		1.90%
Derivative, Basis Spread on Variable Rate		2.50%
Tranche G [Member] | Interest rate swap beginning December 31, 2021 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.60%
Derivative, Variable Interest Rate		3.10%
Derivative, Basis Spread on Variable Rate		2.50%
Tranche G [Member] | Interest rate swap beginning September 30, 2022 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.50%
Derivative, Variable Interest Rate		3.00%
Derivative, Basis Spread on Variable Rate		2.50%
Tranche E | Interest rate swap beginning June 30, 2020 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.00%
Derivative, Variable Interest Rate		2.50%
Derivative, Basis Spread on Variable Rate		2.50%
Tranche E | Interest rate swap beginning June 30, 2022 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.60%
Derivative, Variable Interest Rate		3.10%
Derivative, Basis Spread on Variable Rate		2.50%
Tranche E | Interest rate swap beginning June 29, 2018 [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		5.50%
Derivative, Variable Interest Rate		3.00%
Derivative, Basis Spread on Variable Rate		2.50%
[1]	Refer to Note 20, "Fair Value Measurements," for the consolidated balance sheet classification of our interest rate swap and cap agreements.
[2]	The increase in the interest rate swap liability is primarily attributable to a downward trend in LIBOR during fiscal 2020.

DERIVATIVES AND HEDGING ACTIV_5

DERIVATIVES AND HEDGING ACTIVITIES - Schedule of Notional Amounts (Details) $ in Millions	Sep. 30, 2020USD ($)
Tranche E | Interest rate swap beginning June 29, 2018 [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 500
Tranche E | Interest rate swap beginning June 30, 2020 [Member]
Derivative [Line Items]
Derivative, Notional Amount	750
Tranche E | Interest rate swap beginning June 30, 2022 [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,500
Tranche E | Interest Rate Cap [Member]
Derivative [Line Items]
Derivative, Notional Amount	750
Tranche F | Interest rate swap June 28, 2019 [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,000
Tranche F | Interest rate swap beginning June 30, 2021 [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,400
Tranche F | Interest rate cap agreements beginning June 30, 2016
Derivative [Line Items]
Derivative, Notional Amount	400
Tranche G [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	500
Tranche G [Member] | Interest rate swap beginning September 30, 2017 [Member]
Derivative [Line Items]
Derivative, Notional Amount	400
Tranche G [Member] | Interest rate swap beginning December 31, 2021 [Member]
Derivative [Line Items]
Derivative, Notional Amount	900
Tranche G [Member] | Interest rate swap beginning September 30, 2022 [Member]
Derivative [Line Items]
Derivative, Notional Amount	400
Tranche G [Member] | Interest Rate Cap
Derivative [Line Items]
Derivative, Notional Amount	$ 400

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Mar. 30, 2019	Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of ASU 2018-02, adopted October 1, 2018					$ (2)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax		$ 34	$ (36)		(70)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period		4	(379)		4
Other comprehensive loss before reclassification			(22)		(385)
Amounts reclassified from AOCI related to interest rate swap agreements	[1]				4
Interest rate swaps and caps, net of tax			(130)		(239)		$ 94
Pension liability adjustments, net of tax			32		(29)		5
Foreign currency translation adjustments			76		(115)		(10)
Other comprehensive (loss) income, net of tax, attributable to TD Group			(22)		(383)		89
Balance at end of period			(401)		(379)		4
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax		(1)	(1)		9
INCOME TAX PROVISION			87		222		24
Net income			700		892		957
Unrealized (loss) gain on derivatives designated and qualifying as cash flow hedges (2)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of ASU 2018-02, adopted October 1, 2018					(2)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period		67	(172)	[1]	67
Other comprehensive loss before reclassification			(130)	[1]	(241)
Amounts reclassified from AOCI related to interest rate swap agreements					4
Interest rate swaps and caps, net of tax	[1]				(239)
Balance at end of period			(302)	[1]	(172)	[1]	67
Defined benefit pension plan activity (3)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of ASU 2018-02, adopted October 1, 2018					0
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period		(11)	(40)	[2]	(11)
Other comprehensive loss before reclassification			32	[2]	(29)
Amounts reclassified from AOCI related to interest rate swap agreements					0
Pension liability adjustments, net of tax	[2]				(29)
Balance at end of period			(8)	[2]	(40)	[2]	(11)
Currency translation adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period		$ (52)	(167)		(52)
Other comprehensive loss before reclassification			76		(115)
Amounts reclassified from AOCI related to interest rate swap agreements					0
Foreign currency translation adjustments					(115)
Balance at end of period			(91)		(167)		(52)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized (loss) gain on derivatives designated and qualifying as cash flow hedges (2)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest Expense	[3]		(4)		(3)
Losses from settlement of foreign currency forward contracts	[4]		(4)		0
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
INCOME TAX PROVISION			0		(1)
Net income			$ 0				$ 4
Accounting Standards Update 2018-02 [Member] | Currency translation adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of ASU 2018-02, adopted October 1, 2018					$ 0
[1]	Unrealized (loss) gain represents derivative instruments, net of taxes of $36, $70 and $(34) for the fiscal years ended September 30, 2020, 2019 and 2018, respectively.
[2]	Defined benefit pension plan and other post-retirement plan activity represents pension liability adjustments, net of taxes of $(1), $9 and $(1) for the fiscal years ended September 30, 2020, 2019 and 2018, respectively.
[3]	This component of accumulated other comprehensive (loss) income is included in interest expense. Refer to Note 21, “Derivatives and Hedging Activities,” for additional information.
[4]	This component of accumulated other comprehensive (loss) income is included in net sales. Refer to Note 21, “Derivatives and Hedging Activities,” for additional information.

DISCONTINUED OPERATIONS - Narra

DISCONTINUED OPERATIONS - Narrative (Details) - USD ($) $ in Millions	Dec. 20, 2019	Sep. 20, 2019	Jan. 26, 2018	Sep. 30, 2020		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash Provided by (Used in) Investing Activities, Discontinued Operations							$ 11
Goodwill							480
Assets held-for-sale				$ 0		$ 0	962
Liabilities held-for-sale				0		0	157
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAX				(19)		47	51	$ (5)
Cash Provided by (Used in) Operating Activities, Discontinued Operations							35
NET SALES				$ 1,173	[1],[2]	5,103	5,223	3,811
Souriau Sunbank [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents							29
Trade accounts receivable—Net							67
Inventories—Net							88
Prepaid expenses and other							2
Property, plant and equipment—Net							101
Goodwill							480
Other intangibles—Net							194
Other							1
Assets held-for-sale							962
Accounts payable							33
Accrued liabilities							55
Long-term debt							6
Deferred income taxes							42
Other							21
Liabilities held-for-sale							157
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAX						47
Proceeds from Divestiture of Businesses	$ 920
Income from discontinued operations, net of tax						7
Gain (loss) from sale of discontinued operations, net of tax						40
NET SALES						79	199
Income (loss) from discontinued operations, before income taxes						$ 11	17
Discontinued Operation, Tax Effect of Income (Loss) from Discontinued Operation During Phase-out Period							14
Schroth [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAX								(5)
Proceeds from Divestiture of Businesses			$ 61
Income from discontinued operations, net of tax								2
Gain (loss) from sale of discontinued operations, net of tax								(7)
NET SALES								12
Income (loss) from discontinued operations, before income taxes								$ 0
EIT [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses		$ 190
NET SALES							95
Income (loss) from discontinued operations, before income taxes							17
Discontinued Operation, Tax Effect of Income (Loss) from Discontinued Operation During Phase-out Period							$ 1
[1]	Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Souriau-Sunbank and EIT at September 30, 2019, as discontinued operations. Refer to Note 23, “Discontinued Operations,” for additional information.
[2]	The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. Refer to Note 2 “Acquisitions and Divestitures,” for additional information. (3) Net income applicable to TD Group common stockholders represents net income attributable to TD Group less special dividends and dividend equivalent payments. Special dividend and dividend equivalent payments were $185 million, $24 million and $87 million, respectively, for the first quarter ended December 28, 2019, first quarter ended December 29, 2018 and fourth quarter ended September 30, 2019.

DISCONTINUED OPERATIONS - Sched

DISCONTINUED OPERATIONS - Schedule of Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2020		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
NET SALES	$ 1,173	[1],[2]	$ 5,103	$ 5,223	$ 3,811
Income (loss) from discontinued operations, net of tax	(19)		47	51	(5)
Goodwill				480
Assets held-for-sale	0		0	962
Liabilities held-for-sale	$ 0		0	157
Schroth [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
NET SALES					12
Income (loss) from discontinued operations, before income taxes					0
Income tax provision (benefit)					(2)
Income from discontinued operations, net of tax					2
Gain (loss) from sale of discontinued operations, net of tax					(7)
Income (loss) from discontinued operations, net of tax					$ (5)
Souriau Sunbank [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
NET SALES			79	199
Income (loss) from discontinued operations, before income taxes			11	17
Income tax provision (benefit)			4
Income from discontinued operations, net of tax			7
Gain (loss) from sale of discontinued operations, net of tax			40
Income (loss) from discontinued operations, net of tax			$ 47
Cash and cash equivalents				29
Trade accounts receivable—Net				67
Inventories—Net				88
Prepaid expenses and other				2
Property, plant and equipment—Net				101
Goodwill				480
Other intangibles—Net				194
Other				1
Assets held-for-sale				962
Accounts payable				33
Accrued liabilities				55
Long-term debt				6
Deferred income taxes				42
Other				21
Liabilities held-for-sale				157
EIT [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
NET SALES				95
Income (loss) from discontinued operations, before income taxes				17
Souriau Sunbank and EIT
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
NET SALES				294
Income (loss) from discontinued operations, before income taxes				0
Income tax provision (benefit)				(13)
Income from discontinued operations, net of tax				13
Gain (loss) from sale of discontinued operations, net of tax				38
Income (loss) from discontinued operations, net of tax				$ 51
[1]	Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Souriau-Sunbank and EIT at September 30, 2019, as discontinued operations. Refer to Note 23, “Discontinued Operations,” for additional information.
[2]	The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. Refer to Note 2 “Acquisitions and Divestitures,” for additional information. (3) Net income applicable to TD Group common stockholders represents net income attributable to TD Group less special dividends and dividend equivalent payments. Special dividend and dividend equivalent payments were $185 million, $24 million and $87 million, respectively, for the first quarter ended December 28, 2019, first quarter ended December 29, 2018 and fourth quarter ended September 30, 2019.

QUARTERLY FINANCIAL DATA (UNA_3

QUARTERLY FINANCIAL DATA (UNAUDTIED) - Schedule of Quarterly Financial Data (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Sep. 30, 2020		Jun. 27, 2020		Mar. 28, 2020		Dec. 28, 2019		Sep. 30, 2019		Jun. 29, 2019		Mar. 30, 2019		Dec. 29, 2018		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Quarterly Financial Data [Line Items]
NET SALES		$ 1,173	[1],[2]															$ 5,103	$ 5,223	$ 3,811
Gross Profit																		2,647	2,809	2,177
INCOME FROM CONTINUING OPERATIONS																		653	841	962
Income (loss) from discontinued operations, net of tax		(19)																47	51	(5)
Net income attributable to TD Group		$ 82	[1],[2]															$ 699	$ 890	$ 957
Earnings per share from continuing operations—basic and diluted		$ 1.76	[1],[3]															$ 8.14	$ 12.94	$ 16.28
Earnings (Loss) per share from discontinued operations—basic and diluted		$ (0.33)	[1],[3]															0.82	0.90	(0.08)
Net earnings per share - basic and diluted																		$ 8.96	$ 13.84	$ 16.20
TransDigm Group
Quarterly Financial Data [Line Items]
NET SALES	[1],[2]			$ 1,022		$ 1,443		$ 1,465		$ 1,541		$ 1,521		$ 1,168		$ 993
Gross Profit	[1],[2]	$ 536		491		818		801		882		713		650		564
INCOME FROM CONTINUING OPERATIONS		101		(5)		323		234		317		128		200		196
Income (loss) from discontinued operations, net of tax				(1)		(4)		71		32		17		2		0
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Noncontrolling Interest		$ 0		0		0		(1)		(2)		0		0		0
Net income attributable to TD Group	[1],[2]			$ (6)		$ 319		$ 304		$ 347		$ 145		$ 202		$ 196
Earnings per share from continuing operations—basic and diluted	[1],[3]			$ (0.09)		$ 5.63		$ 0.83		$ 4.08		$ 2.27		$ 3.56		$ 3.05
Earnings (Loss) per share from discontinued operations—basic and diluted	[1],[3]			(0.01)		(0.07)		1.24		0.55		0.30		0.04		0
Net earnings per share - basic and diluted	[1]	$ 1.43	[3]	$ (0.10)	[3]	$ 5.56	[2]	$ 2.07	[3]	$ 4.63	[3]	$ 2.57	[3]	$ 3.60	[3]	$ 3.05	[3]
Net Income (Loss) Available to Common Stockholders, Basic		$ 82		$ (6)		$ 319		$ 119		$ 260		$ 145		$ 202		$ 172
[1]	Results adjusted to reflect amounts reclassified to discontinued operations due to the Company’s classification of Souriau-Sunbank and EIT at September 30, 2019, as discontinued operations. Refer to Note 23, “Discontinued Operations,” for additional information.
[2]	The Company’s operating results include the results of operations of acquisitions from the effective date of each acquisition. Refer to Note 2 “Acquisitions and Divestitures,” for additional information. (3) Net income applicable to TD Group common stockholders represents net income attributable to TD Group less special dividends and dividend equivalent payments. Special dividend and dividend equivalent payments were $185 million, $24 million and $87 million, respectively, for the first quarter ended December 28, 2019, first quarter ended December 29, 2018 and fourth quarter ended September 30, 2019.
[3]	The sum of the earnings per share for the four quarters in a year does not necessarily equal the total year earnings per share due to the weighted average number of shares outstanding in each quarter.

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ in Millions	Oct. 26, 2020	Sep. 30, 2020	Mar. 24, 2020	Sep. 30, 2019
Subsequent Event [Line Items]
Long-term Debt, Gross		$ 19,834		$ 16,713
Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Long-term Debt, Gross		$ 200	$ 200
Revolving Credit Facility [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Interest Payable	$ 0.5
Long-term Debt, Gross	$ 200

Valuation and Qualifying Acco_2

Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		$ 17	$ 5	$ 4
Charged to Costs and Expenses		21	5	2
Acquisitions & Purchase Price Adjustments		(3)	(9)	(1)
Deductions from Reserve	[1]	(4)	(2)	(2)
Balance at End of Period		37	17	5
SEC Schedule 12-09, Inventory Reserve [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period			95
Balance at End of Period				95
Reserve for excess and obsolete inventory
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		124	99	80
Charged to Costs and Expenses		34	17	15
Acquisitions & Purchase Price Adjustments		(37)	(17)	(11)
Deductions from Reserve	[1]	(17)	(9)	(11)
Balance at End of Period		178	124	99
Valuation Allowance of Deferred Tax Assets
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		118	47	33
Charged to Costs and Expenses		15	40	14
Acquisitions & Purchase Price Adjustments		(1)	(31)	0
Deductions from Reserve	[1]	0	0	0
Balance at End of Period		$ 132	$ 118	$ 47
[1]	The amounts in this column represent charge-offs net of recoveries and the impact of foreign currency translation adjustments.

Uncategorized Items - tdg-20200

Label	Element	Value
Common Stock [Member]
Common Stock, Shares, Issued	us-gaap_CommonStockSharesIssued	58,612,028