AAR (AIR) 10-K 12 Jul 17 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	Jun. 30, 2017	Nov. 30, 2016
Document and Entity Information
Entity Registrant Name	AAR CORP
Entity Central Index Key	1,750
Document Type	10-K
Document Period End Date	May 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--05-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 1,355
Entity Common Stock, Shares Outstanding		34,396,501
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Sales:
Sales from products	$ 956.6	$ 934.4	$ 916.7
Sales from services	811	764.5	704.7
Total sales	1,767.6	1,698.9	1,621.4
Cost and operating expenses:
Cost of products	800.7	787.4	891
Cost of services	690.4	673.6	599.6
Selling, general and administrative	196.7	173.2	172.4
Total costs and operating expenses	1,687.8	1,634.2	1,663
Earnings (Loss) from joint ventures	(0.2)	(0.3)	0.2
Operating income (loss)	79.6	64.4	(41.4)
Loss on extinguishment of debt		(0.4)	(44.9)
Interest expense	(5.5)	(6.4)	(27.2)
Interest income	0.2	0.3	0.3
Income (Loss) from continuing operations before provision for income taxes	74.3	57.9	(113.2)
Provision for income tax (benefit)	24.1	19.6	(39.3)
Income (Loss) from continuing operations	50.2	38.3	(73.9)
Income from discontinue operations attributable to AAR	6.3	9.4	84.1
Net income attributable to AAR	$ 56.5	$ 47.7	$ 10.2
Earnings per share - basic:
Earnings (Loss) from continuing operations	$ 1.47	$ 1.10	$ (1.90)
Earnings from discontinued operations	0.19	0.27	2.16
Earnings per share - basic	1.66	1.37	0.26
Earnings per share - diluted:
Earnings (Loss) from continuing operations	1.45	1.10	(1.90)
Earnings from discontinued operations	0.19	0.27	2.14
Earnings per share - diluted	$ 1.64	$ 1.37	$ 0.24

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income	$ 56.5	$ 47.7	$ 10.4
Other comprehensive income, net of tax:
Currency translation adjustments, net of tax	(0.6)		(7.8)
Derivative instruments, net of tax expense of $1.4 in 2015			2.6
Unrecognized pension and post retirement costs, net of tax expense (benefit) of $2.8 in 2017, ($2.1) in 2016, and ($3.2) in 2015	5.1	(4)	(5.9)
Total other comprehensive income (loss), net of tax	4.5	(4)	(11.1)
Comprehensive income (loss)	61	43.7	(0.7)
Less: Comprehensive income attributable to noncontrolling interest			(0.2)
Comprehensive income (loss) attributable to AAR	$ 61	$ 43.7	$ (0.9)

CONSOLIDATED STATEMENTS OF COM4

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Derivative instruments tax expense			$ 1.4
Unrecognized pension and post retirement costs, tax expense (benefit)	$ 2.8	$ (2.1)	$ (3.2)

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	May 31, 2017	May 31, 2016
Current assets:
Cash and cash equivalents	$ 10.3	$ 31.2
Accounts receivable	251.4	248.3
Inventories	483.1	452
Rotable spares and equipment on or available for short-term lease	118	118.3
Deposits, prepaids and other	25.7	31.9
Total current assets	888.5	881.7
Property, plant and equipment, at cost:
Land	4.3	4.5
Buildings and improvements	100.1	99.5
Aircraft, equipment, furniture and fixtures	511.4	571.8
Property, plant and equipment, gross	615.8	675.8
Accumulated depreciation	(413.9)	(437.7)
Property, plant and equipment, net of accumulated depreciation	201.9	238.1
Other assets:
Goodwill	115.4	117.3
Intangible assets, net	32.8	35.8
Equipment on or available for long-term lease	159.6	81.1
Other	105.9	102
Total other assets	413.7	336.2
Total assets	1,504.1	1,456
Current liabilities:
Current maturities of long-term debt	2	12
Accounts and trade notes payable	177.4	166.3
Accrued liabilities	155.7	163.1
Total current liabilities	335.1	341.4
Long-term debt, less current maturities	155.3	136.1
Deferred tax liabilities	37.2	34.3
Other liabilities and deferred income	62.3	78.4
Total noncurrent liabilities	254.8	248.8
Equity:
Preferred stock, $1.00 par value, authorized 250,000 shares; none issued
Common stock, $1.00 par value, authorized 100,000,000 shares; issued 45,175,302 and 44,867,703 shares at cost, respectively	45.2	44.9
Capital surplus	460.8	451.3
Retained earnings	727.9	681.6
Treasury stock, 10,820,844 and 10,353,153 shares at cost, respectively	(279.8)	(267.6)
Accumulated other comprehensive loss	(39.9)	(44.4)
Total equity	914.2	865.8
Total liabilities and equity	$ 1,504.1	$ 1,456

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	May 31, 2017	May 31, 2016
CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, authorized shares	250,000	250,000
Preferred stock, issued shares	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, authorized shares	100,000,000	100,000,000
Common stock, issued shares	45,175,302	44,867,703
Treasury stock, shares	10,820,844	10,353,153

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total AAR Stockholders' Equity	Common Stock	Capital Surplus	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest	Total
Balance at May. 31, 2014	$ 999.5	$ 44.7	$ 436.4	$ 646	$ (98.3)	$ (29.3)	$ 1.2	$ 1,000.7
Increase (Decrease) in Stockholders' Equity
Net income	10.2			10.2			0.2	10.4
Cash dividends	(11.9)			(11.9)			(0.6)	(12.5)
Stock option activity	6.3		2.1		4.2			6.3
Restricted stock activity	4.2	0.2	4.7		(0.7)			4.2
Repurchase of shares	(151.5)				(151.5)			(151.5)
Other	(0.6)		(0.6)				$ (0.8)	(1.4)
Other comprehensive income (loss), net of tax	(11.1)					(11.1)		(11.1)
Balance at May. 31, 2015	845.1	44.9	442.6	644.3	(246.3)	(40.4)		845.1
Increase (Decrease) in Stockholders' Equity
Net income	47.7			47.7				47.7
Cash dividends	(10.4)			(10.4)				(10.4)
Stock option activity	6.7		4.4		2.3			6.7
Restricted stock activity	(0.3)		4.5		(4.8)			(0.3)
Repurchase of shares	(18.8)				(18.8)			(18.8)
Other	(0.2)		(0.2)					(0.2)
Other comprehensive income (loss), net of tax	(4)					(4)		(4)
Balance at May. 31, 2016	865.8	44.9	451.3	681.6	(267.6)	(44.4)		865.8
Increase (Decrease) in Stockholders' Equity
Net income	56.5			56.5				56.5
Cash dividends	(10.2)			(10.2)				(10.2)
Stock option activity	12		3.1		8.9			12
Restricted stock activity	5.4	0.3	6.4		(1.3)			5.4
Repurchase of shares	(19.8)				(19.8)			(19.8)
Other comprehensive income (loss), net of tax	4.5					4.5		4.5
Balance at May. 31, 2017	$ 914.2	$ 45.2	$ 460.8	$ 727.9	$ (279.8)	$ (39.9)		$ 914.2

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Cash flows provided from (used in) operating activities:
Net income	$ 56.5	$ 47.7	$ 10.4
Less: Income from discontinued operations	(6.3)	(9.4)	(84.3)
Income (Loss) from continuing operations	50.2	38.3	(73.9)
Adjustments to reconcile net income to net cash provided from (used in) operating activities:
Depreciation and intangible amortization	52.9	51.1	58
Impairment charges			53
Amortization of stock-based compensation	11	6.7	7.4
Amortization of overhaul costs	18.1	20.8	23.2
Deferred tax provision (benefit)	0.6	4.8	(52.6)
Gain on sale of product line	(2.6)
Loss on extinguishment of debt		0.4	44.9
Changes in certain assets and liabilities, net of acquisitions:
Accounts receivable	(4)	(14.1)	(6.5)
Inventories	(18.8)	(24.6)	(29.2)
Rotable spares and equipment on or available for short-term lease	2.3	(7.4)	6.6
Equipment on or available for long-term lease	(82.5)	(10.2)	6.2
Accounts and trade notes payable	14.1	19.9	3
Accrued and other liabilities	3.3	(30.2)	46.4
Other, primarily program and overhaul costs	(20.4)	(22.9)	(0.1)
Net cash provided from operating activities-continuing operations	24.2	32.6	86.4
Net cash used in operating activities-discontinued operations	(2.4)	(0.5)	(129.4)
Net cash provided from (used in) operating activities	21.8	32.1	(43)
Cash flows used in investing activities:
Property, plant and equipment expenditures	(33.6)	(88.9)	(42.1)
Proceeds from asset disposals	18.7	45.1	46.8
Payments for acquisitions	(12.5)	(4.8)	(1)
Other	(2.7)	1	3.5
Net cash provided by (used in) investing activities-continuing operations	(30.1)	(47.6)	7.2
Net cash provided from investing activities- discontinued operations		30.7	682
Net cash provided from (used in) investing activities	(30.1)	(16.9)	689.2
Cash flows used in financing activities:
Short-term borrowings (repayments), net	21	60	(80)
Reduction in long-term borrowings	(10)	(70.6)	(394.8)
Cash dividends	(10.2)	(10.4)	(11.9)
Premium paid on early retirement of debt			(45.6)
Purchase of treasury stock	(19.8)	(18.8)	(151.5)
Other	6.9	1.4	6.3
Net cash used in financing activities- continuing operations	(12.1)	(38.4)	(677.5)
Net cash used in financing activities - discontinued operations			(0.6)
Net cash used in financing activities	(12.1)	(38.4)	(678.1)
Effect of exchange rate changes on cash	(0.5)	(0.3)	(2.6)
Decrease in cash and cash equivalents	(20.9)	(23.5)	(34.5)
Cash and cash equivalents, beginning of year	31.2	54.7	89.2
Cash and cash equivalents, end of year	$ 10.3	$ 31.2	$ 54.7

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	May 31, 2017
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	1. Summary of Significant Accounting Policies Description of Business AAR CORP. is a diversified provider of services and products to the worldwide commercial aviation and government and defense markets. Services and products include: aviation supply chain and parts support programs; maintenance, repair and overhaul of airframes, landing gear, and certain other airframe components; design and manufacture of specialized pallets, shelters, and containers; expeditionary airlift services; aircraft modifications and aircraft and engine sales and leasing. We serve commercial, defense and governmental aircraft fleet operators, original equipment manufacturers, and independent service providers around the world, and various other domestic and foreign military customers. Principles of Consolidation The accompanying Consolidated Financial Statements include the accounts of the Company and its majority-owned subsidiaries after elimination of intercompany accounts and transactions. The equity method of accounting is used for investments in other companies in which we have significant influence; generally this represents common stock ownership of at least 20% and not more than 50% (see Note 10 for a discussion of aircraft joint ventures). Revenue Recognition Sales and related cost of sales for product sales are recognized upon shipment of the product to the customer. Our standard terms and conditions provide that title passes to the customer when the product is shipped to the customer. Sales of certain defense products are recognized upon customer acceptance, which includes transfer of title. Under the majority of our expeditionary airlift services contracts, we are paid and record as revenue a fixed daily amount per aircraft for each day an aircraft is available to perform airlift services. In addition, we are paid and record as revenue an amount which is based on number of hours flown. Sales from services and the related cost of services are generally recognized when customer-owned material is shipped back to the customer. We have adopted this accounting policy because at the time the customer-owned material is shipped back to the customer; all services related to that material are complete as our service agreements generally do not require us to provide services at customer sites. Furthermore, serviced units are typically shipped to the customer immediately upon completion of the related services. Sales and related cost of sales for certain large airframe maintenance contracts and performance-based logistics programs are recognized by the percentage of completion method, based on the relationship of costs incurred to date to the estimated total costs. When our experience and projections indicate adjustments to the estimated margin are required, changes are recognized using the cumulative catch-up method with the impact of the change from inception to date recorded in the current period. Net favorable cumulative catch-up adjustments recognized during fiscal 2017, 2016, and 2015 were $8.5 million, $3.7 million, and $2.5 million, respectively. Lease revenues are recognized as earned. Income from monthly or quarterly rental payments is recorded in the pertinent period according to the lease agreement. However, for leases that provide variable rents, we recognize lease income on a straight-line basis. In addition to a monthly lease rate, some engine leases require an additional rental amount based on the number of hours the engine is used in a particular month. Lease income associated with these contingent rentals is recorded in the period in which actual usage is reported to us by the lessee, which is normally the month following the actual usage. Certain supply chain management programs we provide to our customers contain multiple elements or deliverables, such as program and warehouse management, parts distribution, and maintenance and repair services. We recognize revenue for each element or deliverable that can be identified as a separate unit of accounting at the time of delivery based upon the relative fair value of the products and services. Included in accounts receivable as of May 31, 2017 and 2016, are $14.5 million and $29.8 million, respectively, of unbilled accounts receivable related to our KC-10 supply agreement. These unbilled accounts receivable relate to costs we have incurred on parts that were requested and accepted by our customer to support the program. These costs have not been billed by us because the customer has not issued the final paperwork necessary to allow for billing. In June 2016, the U.S. Air Force awarded the new contract for the KC-10 Extender Contractor Logistics Support Program ("KC-10 Program") to a competitor. Our principal services under the prior contract for the KC-10 Program were completed in January 2017; however, we expect limited services will continue for an unspecified period of time. Sales for the KC-10 Program during fiscal 2017, 2016 and 2015 were $110.6 million, $148.1 million, and $111.4 million, respectively. Gross profit for the KC-10 Program during fiscal 2017, 2016 and 2015 was $3.7 million, $12.0 million, and $4.5 million, respectively. Allowance for Doubtful Accounts We maintain an allowance for doubtful accounts to reflect the expected uncollectibility of accounts receivable based on past collection history and specific risks identified among uncollected accounts. In determining the required allowance, we consider factors such as general and industry-specific economic conditions, customer credit history, and our customers' current and expected future financial performance. The majority of our customers are recurring customers with an established payment history. Certain customers are required to undergo an extensive credit check prior to delivery of products or services. Goodwill and Other Intangible Assets In accordance with Accounting Standards Codification ("ASC") 350, Intangibles—Goodwill and Other , goodwill and other intangible assets deemed to have indefinite lives are not amortized, but are subject to annual impairment tests. We review and evaluate our goodwill and indefinite life intangible assets for potential impairment at a minimum annually, on May 31, or more frequently if circumstances indicate that impairment is possible. We utilize both the qualitative approach and the two-step quantitative approach to evaluate goodwill for impairment. In the first step of the quantitative approach, we compare the fair value of the reporting unit with its carrying value, including goodwill. If the estimated fair value of the reporting unit is less than its carrying value, we would be required to complete a second step to determine the amount of goodwill impairment. The second step of the test requires the allocation of the reporting unit's fair value to its assets and liabilities, including any unrecognized intangible assets, in a hypothetical analysis that calculates the implied fair value of goodwill as if the reporting unit was being acquired in a business combination. If the implied fair value of goodwill is less than the carrying value, the difference is recorded as an impairment loss. As of May 31, 2017, we have five reporting units with only four of the reporting units assigned goodwill. Our four reporting units with goodwill include two in our Aviation Services segment (Aviation Supply Chain and Maintenance, Repair, and Overhaul) and two in our Expeditionary Services segment (Airlift and Mobility). We utilized the qualitative assessment approach for the two Aviation Services reporting units and the two-step quantitative approach for the two Expeditionary Services reporting units. We performed the annual qualitative analysis for the two Aviation Services reporting units and concluded it was more likely than not that the fair value of each reporting unit exceeded their carrying values, and thus no impairment charge was recorded. Step one of the quantitative goodwill impairment test was completed for the two Expeditionary Services reporting units and the estimated fair value for each reporting unit exceeded its carrying value. Accordingly, there was no indication of impairment and the second step was not performed. We estimate the fair value of each Expeditionary Services reporting unit using an income approach based on discounted cash flows. The assumptions we used to estimate the fair value of these reporting units are based on historical performance, as well as forecasts used in our current business plan, and require considerable management judgment. We use a discount rate based on our consolidated weighted average cost of capital which is adjusted for each of our reporting units based on their specific risk and size characteristics. The fair value measurements used for our goodwill impairment testing use significant unobservable inputs, which reflect our own assumptions about the inputs that market participants would use in measuring fair value. The fair value of our reporting units is also impacted by our overall market capitalization and may be impacted by volatility in our stock price and assumed control premium, among other items. Changes in the carrying amount of goodwill by segment for fiscal 2017 and 2016 are as follows: Aviation Expeditionary Total Balance as of May 31, 2015 $ $ $ Acquisition — Deferred tax adjustments ) — ) Foreign currency translation adjustments ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2016 Foreign currency translation adjustments ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2017 $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Intangible assets with finite useful lives are amortized on a straight-line basis over their estimated useful lives. Intangible assets, other than goodwill, are comprised of the following: May 31, 2017 Gross Accumulated Net Amortizable intangible assets: Customer relationships $ $ ) $ Developed technology ) Lease agreements ) FAA certificates ) Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ) Unamortized intangible assets: Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ May 31, 2016 Gross Accumulated Net Amortizable intangible assets: Customer relationships $ $ ) $ Developed technology ) Lease agreements ) FAA certificates ) Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ) Unamortized intangible assets: Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Customer relationships are being amortized over 10-20 years, developed technology is being amortized over 7-15 years, lease agreements are being amortized over 5-18 years, and the FAA certificates are being amortized over 20 years. Amortization expense recorded during fiscal 2017, 2016 and 2015 was $4.3 million, $4.4 million, and $4.6 million, respectively. The estimated aggregate amount of amortization expense for intangible assets in each of the next five fiscal years is $4.5 million in 2018, $3.8 million in 2019, $3.5 million in 2020, $3.5 million in 2021 and $2.7 million in 2022. Foreign Currency Our foreign subsidiaries utilize the local currency as their functional currency. All balance sheet accounts of foreign subsidiaries transacting business in currencies other than the U.S. dollar are translated at year-end exchange rates. Revenues and expenses are translated at average exchange rates during the year. Translation adjustments are excluded from the results of operations and are recorded in stockholders' equity as a component of accumulated other comprehensive loss until such subsidiaries are liquidated. Cash and Cash Equivalents Cash and cash equivalents consist of highly liquid instruments which have original maturities of three months or less when purchased. Financial Instruments and Concentrations of Market or Credit Risk Financial instruments that potentially subject us to concentrations of market or credit risk consist principally of trade receivables. While our trade receivables are diverse and represent a number of entities and geographic regions, the majority are with the U.S. Department of Defense and its contractors and entities in the aviation industry. Accounts receivable due from the U.S. Department of Defense were $43.0 million and $43.7 million at May 31, 2017 and 2016, respectively. Additionally, included in accounts receivable as of May 31, 2017 and 2016, are $25.5 million and $42.4 million, respectively, of accounts receivable from a large defense contractor. We perform regular evaluations of customer payment experience, current financial condition, and risk analysis. We may require collateral in the form of security interests in assets, letters of credit, and/or obligation guarantees from financial institutions for transactions executed on other than normal trade terms. The carrying amounts of cash and cash equivalents, accounts receivable, and accounts and trade notes payable approximate fair value because of the short-term maturity of these instruments. The carrying value of long-term debt bearing a variable interest rate approximates fair value. Fair value estimates are made at a specific point in time based on relevant market information about the financial instrument. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. Changes in assumptions could significantly affect the estimates. Inventories Inventories are valued at the lower of cost or market (estimated net realizable value). Cost is determined by the specific identification, average cost, or first-in, first-out methods. From time-to-time, we purchase aircraft and engines for disassembly to individual parts and components. Costs are assigned to these individual parts and components utilizing list prices from original equipment manufacturers and recent sales history. The following is a summary of inventories: May 31, 2017 2016 Raw materials and parts $ $ Work-in-process Aircraft and engine parts, components and finished goods Aircraft held for sale and related support parts ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ We classify certain aircraft from our expeditionary airlift business as assets held for sale at the time management commits to a plan to sell the aircraft, changes to the planned sale are not likely, the aircraft are actively marketed and available for immediate sale, and the sale is expected to be completed within one year. Upon designation of an aircraft as held for sale, we record the aircraft's value at the lower of its carrying value or its estimated fair value, less estimated costs to sell. Assets held for sale are not depreciated. Aircraft may be classified as assets held for sale for more than one year as we continue to actively market the aircraft at reasonable prices. Certain aircraft types we currently have available for sale are specifically designed for particular functions which limits the marketability of those assets. During fiscal 2015, we recognized impairment charges of $8.9 million reflecting the decrease in fair value for certain aircraft held for sale and related rotable assets. During the fourth quarter of fiscal 2015, we entered into a sale-leaseback transaction for our two S-92 rotary-wing aircraft resulting in the recognition of a loss of $1.1 million. We received sales proceeds of $40.3 million in fiscal 2015 which were deferred as a sale-leaseback advance pending completion of the sale transactions. Both of the S-92 aircraft sales were completed in fiscal 2016 and the related leases ended in fiscal 2017. Equipment under Leases Lease revenue is recognized as earned. The cost of the asset under lease is the original purchase price plus overhaul costs. Depreciation for aircraft is computed using the straight-line method over the estimated service life of the equipment. The balance sheet classification of equipment under lease is generally based on lease term, with fixed-term leases less than twelve months generally classified as short-term and all others generally classified as long-term. Equipment on short-term lease includes aircraft engines and parts on or available for lease to satisfy customers' immediate short-term requirements. The leases are renewable with fixed terms, which generally vary from one to twelve months. In conjunction with our decision to exit certain product lines in our landing gear business, we recognized an impairment charge of $17.7 million related to rotable assets in fiscal 2015. Equipment on long-term lease consists of engines on lease with commercial airlines generally for more than twelve months and rotable parts used to support long-term supply chain programs. The rotable parts included in equipment on long-term lease are being depreciated on a straight-line basis over their estimated useful lives. During the fourth quarter of fiscal 2015, we sold our two remaining wholly-owned aircraft which were on long-term leases for $11.0 million which resulted in a loss on sale of $14.8 million. Future rent due to us under non-cancelable leases during each of the next five fiscal years is $31.6 million in 2018, $31.3 million in 2019, $31.2 million in 2020, $30.6 million in 2021, and $30.6 million in 2022. Property, Plant and Equipment We record property, plant and equipment at cost. Depreciation is computed on the straight-line method over useful lives of 10-40 years for buildings and improvements and 3-10 years for equipment, furniture and fixtures, and capitalized software. Aircraft, major components in service, and associated rotable assets to support our expeditionary airlift services are depreciated over their estimated useful lives, which is generally 7-30 years. Leasehold improvements are amortized over the shorter of the estimated useful life or the term of the applicable lease. Repair and maintenance expenditures are expensed as incurred. Upon sale or disposal, cost and accumulated depreciation are removed from the accounts, and related gains and losses are included in results of operations. In accordance with ASC 360, Property, Plant and Equipment , we are required to test for impairment of long-lived assets whenever events or changes in circumstances indicate the carrying value of an asset may not be recoverable from its undiscounted cash flows. We utilize certain assumptions to estimate future undiscounted cash flows, including demand for our services, future market conditions and trends, business development pipeline of opportunities, current and future lease rates, lease terms, and residual values. Income Taxes We are subject to income taxes in the U.S., state, and several foreign jurisdictions. In the ordinary course of business, there can be transactions and calculations where the ultimate tax determination is uncertain. We recognize deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns in accordance with applicable accounting guidance for accounting for income taxes, using currently enacted tax rates in effect for the year in which the differences are expected to reverse. We record a valuation allowance when necessary to reduce deferred tax assets to the amount expected to be realized. Deferred tax assets are reduced by a valuation allowance if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. Both positive and negative evidence are considered in forming our judgment as to whether a valuation allowance is appropriate, and more weight is given to evidence that can be objectively verified. Valuation allowances are reassessed whenever there are changes in circumstances that may cause a change in judgment. The accounting for uncertainty in income taxes requires a more-likely-than-not threshold for financial statement recognition of tax positions taken or expected to be taken in a tax return. Where necessary, we record a liability for the difference between the benefit recognized for financial statement purposes and the tax position taken or expected to be taken on our tax return. To the extent that our assessment of such tax positions changes, the change in estimate is recorded in the period in which the determination is made. Supplemental Information on Cash Flows Supplemental information on cash flows is as follows: For the Year Ended 2017 2016 2015 Interest paid $ $ $ Income taxes paid Income tax refunds and interest received During fiscal 2017, treasury stock increased $12.2 million reflecting the repurchase of common shares of $19.8 million, restricted stock grants of $1.3 million and the re-issuance of shares upon exercise of stock options, net of shares withheld to satisfy statutory tax obligations, of $8.9 million. During fiscal 2016, treasury stock increased $21.3 million reflecting the repurchase of common shares of $18.8 million, restricted stock grants of $4.8 million and the re-issuance of shares upon exercise of stock options, net of shares withheld to satisfy statutory tax obligations, of $2.3 million. On May 29, 2015, we repurchased 4,185,960 shares of our common stock at a price of $31.90 per share pursuant to a tender offer utilizing $133.5 million cash on hand. Fees and expenses of $1.2 million were incurred related to the tender offer and were recorded in treasury stock. In addition to the tender offer, we also repurchased common shares of $16.8 million and re-issued shares upon exercise of stock options, net of shares withheld to satisfy statutory tax obligations, of $3.6 million during fiscal 2015. Use of Estimates We have made estimates and utilized certain assumptions relating to the reporting of assets and liabilities and the disclosures of contingent liabilities to prepare these Consolidated Financial Statements in conformity with accounting principles generally accepted in the United States. Actual results could differ from those estimates. New Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, which provides guidance for revenue recognition. This ASU affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of non-financial assets. This ASU will supersede the revenue recognition requirements in ASC 605, Revenue Recognition, and most industry-specific guidance. This ASU will also supersede certain cost guidance included in Subtopic 605-35, Revenue Recognition—Construction-Type and Production-Type Contracts. In August 2015, the FASB issued ASU No. 2015-14 which deferred the effective date of the new standard by one year which will make the new standard effective for us beginning June 1, 2018. The ASU may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of initial application. We continue to gain an understanding of the standard's revenue recognition model and are in the process of analyzing and documenting our significant customer contracts to evaluate the potential impact of the adoption of this new ASU. We have not yet selected a transition method for adoption nor determined the potential effect on our accounting policies and consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases. This ASU amends the existing accounting standards for lease accounting, including requiring lessees to recognize most leases on their balance sheets, including those classified as operating leases under the current accounting guidance. In addition, this ASU will require new qualitative and quantitative disclosures about the Company's leasing activities. This new standard will be effective for us beginning June 1, 2019 with early adoption permitted. This ASU requires a modified retrospective transition approach for all leases existing at, or entered into after, the date of initial application, with an option to use certain transition relief. We are in the preliminary phases of assessing the effect of this ASU on our portfolio of leases. While this assessment continues, we have not yet selected a transition date nor have we determined the effect of this ASU on our consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, "Improvements to Employee Share-Based Payment Accounting," which amends ASC Topic 718, Compensation—Stock Compensation. This ASU requires excess tax benefits or deficiencies for share-based payments be recorded in the period shares vest as income tax expense or benefit, rather than within Capital surplus . Cash flows related to excess tax benefits will be included in operating activities and will no longer be classified as a financing activity. This ASU will be effective for us beginning June 1, 2017 and no material impact on our financial statements is expected.

Discontinued Operations

Discontinued Operations	12 Months Ended
	May 31, 2017
Discontinued Operations
Discontinued Operations	2. Discontinued Operations On March 26, 2015, we completed the sale of our Telair Cargo Group to TransDigm, Inc. The Telair Cargo Group was comprised of Telair International, Telair US, and Nordisk Aviation Products. Cash received at closing in the fourth quarter of fiscal 2015 before fees and expenses was $705 million. The sale also allowed for contingent consideration of up to $35 million based on the occurrence of certain post-closing events related to the A400M cargo system. We recognized a pre-tax gain on the sale (net of transaction expenses and fees) of $198.6 million in the fourth quarter of fiscal 2015. In the first quarter of fiscal 2016, we recognized a gain of $27.7 million net of expenses representing the receipt of the contingent consideration related to the A400M cargo system. During fiscal 2015, we also announced our intention to sell our Precision Systems Manufacturing ("PSM") businesses comprised of our metal and composite machined and fabricated parts manufacturing operations. We recognized impairment charges of $57.5 million during fiscal 2015 to reduce the carrying value of the PSM business's net assets to their expected value at the time of sale. During the first quarter of fiscal 2017, we decided to retain our composite manufacturing operations within our Expeditionary Services segment as a product line within our mobility products business. As a result, we reclassified our composite manufacturing operations into continuing operations for all periods presented which included $25.6 million of impairment charges previously classified in discontinued operations which are now classified as Cost of products in our fiscal 2015 Consolidated Statement of Income. Also during the first quarter of fiscal 2017, we decided to shut down our metal machining operation which had been available for sale. The shutdown of the metal machining operation was completed prior to the end of the first quarter of fiscal 2017. Telair Cargo Group and PSM's metal machining operation are reported as discontinued operations in the Consolidated Statements of Income for all periods presented. No amounts for general corporate overhead were allocated to discontinued operations during the periods presented. Interest expense allocated to discontinued operations was $8.5 million for fiscal 2015. No interest expense was allocated to discontinued operations in fiscal 2017 and fiscal 2016. Liabilities of discontinued operations of $6.9 million and $12.5 million at May 31, 2017 and 2016, respectively, were classified as Accrued liabilities on the Consolidated Balance Sheet. Income from discontinued operations was comprised of the following: For the Year Ended 2017 2016 2015 Sales $ $ $ Cost of sales Selling, general and administrative expenses Interest expense, net. — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating income (loss) from discontinued operations ) ) Gain on sale of Telair Cargo Group — PSM Impairment charges — — ) Provision for income taxes (benefit) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income from discontinued operations Income attributable to noncontrolling interest — — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income from discontinued operations attributable to AAR $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ During the third quarter of fiscal 2016, we recognized $2.8 million of income tax expense in discontinued operations related to changes in estimates associated with tax provision to federal income tax return filing differences. During the fourth quarter of fiscal 2017, we recognized an income tax benefit in discontinued operations of $6.7 million for an effective settlement of a previously reserved tax position. Unless otherwise noted, amounts and disclosures throughout these Notes to Consolidated Financial Statements relate to our continuing operations.

Financing Arrangements

Financing Arrangements	12 Months Ended
	May 31, 2017
Financing Arrangements
Financing Arrangements	3. Financing Arrangements Debt Outstanding A summary of the carrying amount of our debt is as follows: May 31, 2017 2016 Revolving Credit Facility expiring November 1, 2021 with interest payable monthly $ $ Industrial revenue bond (secured by property, plant and equipment) due August 1, 2018 with interest payable monthly Note payable due March 9, 2017 with floating interest rate, payable semi-annually on June 1 and December 1 — Capital lease obligations ​ ​ ​ ​ ​ ​ ​ ​ Total debt Current maturities of debt ) ) Debt issuance costs, net ) ) ​ ​ ​ ​ ​ ​ ​ ​ Long-term debt $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At May 31, 2017, our variable rate and fixed rate debt had a fair value that approximates the carrying value of $156.0 million and are classified as Level 2 in the fair value hierarchy. During fiscal 2016, the Company entered into capital leases in the amount of $5.1 million related to new aircraft and IT equipment. We have omitted substantially all of the required disclosures as the capital leases are not material to our consolidated financial position or results of operations. We maintain a Revolving Credit Facility with various financial institutions, as lenders and Bank of America, N.A., as administrative agent for the lenders which provides the Company an aggregate revolving credit commitment amount of $500 million. The Company, under certain circumstances, has the ability to request an increase to the revolving credit commitment by an aggregate amount of up to $250 million, not to exceed $750 million in total. On November 1, 2016, we entered into an amendment to our Revolving Credit Facility which extended the maturity of the Revolving Credit Facility to November 1, 2021, eliminated the condition of no material adverse change for credit extensions and modified certain other provisions. Borrowings under the Revolving Credit Facility bear interest at the offered Eurodollar Rate plus 100 to 200 basis points based on certain financial measurements if a Eurodollar Rate loan, or at the offered fluctuating Base Rate plus 0 to 100 basis points based on certain financial measurements if a Base Rate loan. Our financing arrangements also requires us to comply with leverage and interest coverage ratios and comply with certain affirmative and negative covenants, including those relating to financial reporting and notification, payment of indebtedness, cash dividends, taxes and other obligations, compliance with applicable laws, and limitations on additional liens, indebtedness, acquisitions, investments and disposition of assets. The Revolving Credit Facility also requires our significant domestic subsidiaries, and any subsidiaries that guarantee our other indebtedness, to provide a guarantee of payment under the Revolving Credit Facility. At May 31, 2017, we were in compliance with the financial and other covenants in our financing agreements. Borrowing activity under the Revolving Credit Facility during fiscal 2017, 2016 and 2015 is as follows: For the Year Ended May 31, 2017 2016 2015 Maximum amount borrowed $ $ $ Average daily borrowings Average interest rate during the year % % % We also have $9.6 million available under foreign lines of credit. 7.25% Senior Notes due 2022 On April 30, 2015, we redeemed our $325 million 7.25% Senior Notes due 2022 for $370.6 million. We recognized a loss on extinguishment of debt of $44.9 million comprised of a make-whole premium of $45.6 million and unamortized deferred financing costs of $6.2 million, partially offset by an unamortized net premium of $6.9 million. Convertible Notes The interest expense associated with the convertible notes, which were paid in full in the fourth quarter of fiscal 2016, was as follows: For the Year 2016 2015 Coupon interest $ $ Amortization of deferred financing fees Amortization of discount ​ ​ ​ ​ ​ ​ ​ ​ Interest expense related to convertible notes $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	May 31, 2017
Derivative Instruments and Hedging Activities
Derivative Instruments and Hedging Activities	4. Derivative Instruments and Hedging Activities We are exposed to interest rate risk associated with fluctuations in interest rates on our variable rate debt. Prior to the fourth quarter of fiscal 2015, we utilized two derivative financial instruments to manage our variable interest rate exposure. We utilized a floating-to-fixed interest rate swap and an interest rate cap agreement with each hedging $50.0 million of notional principal interest under our Revolving Credit Facility. In connection with the Amendment of our Revolving Credit Facility, we settled our floating-to-fixed interest rate swap and interest rate cap agreements in the fourth quarter of fiscal 2015 for approximately $2.6 million. Prior to the settlement, the derivatives instruments were classified as cash flow hedges with gains and losses on the derivative instruments included in other comprehensive loss. We recognized gains and losses on our derivative instruments as an adjustment to interest expense in the period the hedged interest payment affected earnings. We recognized a loss of $2.0 million in fiscal 2015 related to the reclassification of previously unrealized losses in accumulated other comprehensive loss.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	May 31, 2017
Stock-Based Compensation
Stock-Based Compensation	5. Stock-Based Compensation We have granted stock-based awards under the AAR CORP. 2013 Stock Plan (the "2013 Stock Plan") and the AAR CORP. Stock Benefit Plan ("Stock Benefit Plan") each of which has been approved by our stockholders. No further awards will be made under the Stock Benefit Plan. Under the 2013 Stock Plan, we are authorized to issue stock options to employees and non-employee directors that allow the grant recipients to purchase shares of common stock at a price not less than the fair market value of the common stock on the date of grant. Generally, stock options awarded expire ten years from the date of grant and are exercisable in three, four or five equal annual increments commencing one year after the date of grant. In addition to stock options, the 2013 Stock Plan also provides for the grant of restricted stock awards and performance-based restricted stock awards. The number of performance-based awards earned, subject to vesting, is based on achievement of certain Company-wide or segment financial goals or stock price targets. The 2013 Stock Plan also provides for the grant of stock appreciation units and restricted stock units; however, to date, no such awards have been granted. Restricted stock grants are designed, among other things, to align employee interests with the interests of stockholders and to encourage the recipient to build a career with us. Restricted stock typically vests over periods of one to five years from date of grant. Restricted stock grants may be performance-based with vesting to occur over periods of three to five years. All restricted stock that has been granted and, if performance-based, earned according to performance criteria carries full dividend and voting rights, regardless of whether it has vested. Substantially all stock options and restricted stock are subject to forfeiture prior to vesting if the employee's employment terminates for any reason other than death, disability or retirement. Since inception, a total of 11,149,000 shares have been granted under the Stock Benefit Plan. Subsequent to stockholder approval of the 2013 Stock Plan, we have granted a total of 2,018,000 shares under the 2013 Stock Plan. All future stock awards will be made under the 2013 Stock Plan. There were 2,689,733 shares available for grant under the 2013 Stock Plan as of May 31, 2017. Stock Options During fiscal 2017 and 2016, we granted stock options with respect to 687,000 shares and 488,767 shares, respectively. No stock options were granted during fiscal 2015. The weighted average fair value per share of stock options granted during fiscal 2017 and 2016 was $6.50 and $7.48, respectively. The fair value of each stock option grant was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions: Stock Options 2017 2016 Risk-free interest rate % % Expected volatility of common stock % % Dividend yield % % Expected option term in years The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. The expected volatility is based on historical volatility of our common stock, and the expected option term represents the period of time that the stock options granted are expected to be outstanding based on historical exercise trends. The dividend yield represents our anticipated cash dividends at the grant date over the expected option term. A summary of stock option activity for the three years ended May 31, 2017 consisted of the following (shares in thousands): 2017 2016 2015 Shares Weighted Shares Weighted Shares Weighted Outstanding at beginning of year $ $ $ Granted $ $ — $ — Exercised ) $ ) $ ) $ Cancelled ) $ ) $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at end of year $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options exercisable at end of year $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The total fair value of stock options that vested during fiscal 2017, 2016, and 2015 was $3.5 million, $2.7 million, and $3.1 million, respectively. The total intrinsic value of stock options exercised during fiscal 2017, 2016, and 2015 was $4.7 million, $1.0 million, and $11.1 million, respectively. The aggregate intrinsic value of options outstanding was $27.8 million and $7.4 million as of May 31, 2017 and 2016, respectively. The tax benefit realized from stock options exercised during fiscal 2017, 2016, and 2015 was $1.2 million, $0.2 million, and $2.4 million, respectively. Expense recognized in selling, general and administrative expenses for stock options during fiscal 2017, 2016, and 2015 was $4.6 million, $3.5 million, and $2.7 million, respectively. As of May 31, 2017, we had $5.5 million of unrecognized compensation expense related to stock options that will be amortized over an average period of 0.8 years. The following table provides additional information regarding stock options outstanding as of May 31, 2017 (shares in thousands): Options Outstanding Options Exercisable Option Number Weighted-Average Weighted- Number Weighted- $12.00 - $20.00 $ $ $20.01 - $26.00 $ $ $26.01 - $34.50 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Restricted Stock We provide executives and other key employees an opportunity to be awarded performance-based and time-based restricted stock. The performance-based awards are contingent upon the achievement of certain performance objectives, including cumulative net income and average return on capital over a three-year performance period. During fiscal 2017, 2016, and 2015, we granted 212,583, 119,929, and 188,125 of performance-based restricted shares, respectively. Time-based restricted shares of 39,100, 42,557, and 97,581 were granted to executives and key employees during fiscal 2017, 2016, and 2015, respectively. We also award time-based restricted stock to our non-employee directors as part of their annual compensation. Time-based restricted shares of 50,625, 47,083, and 45,000 were granted to members of the Board of Directors during fiscal 2017, 2016, and 2015, respectively. The fair value of restricted shares is the market value of our common stock on the date of grant. Expense recognized in selling, general and administrative expenses for all restricted share programs during fiscal 2017, 2016, and 2015 was $6.4 million, $3.2 million, and $4.7 million, respectively. Restricted share activity during the fiscal year ended May 31, 2017 was as follows (shares in thousands): Number of Weighted Average Nonvested at May 31, 2016 $ Granted $ Vested ) $ Forfeited ) $ ​ ​ ​ ​ ​ ​ ​ ​ Nonvested at May 31, 2017 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of May 31, 2017 we had $5.5 million of unearned compensation related to restricted shares that will be amortized to expense over a weighted average period of 2.1 years. Shareholders' Rights Plan Pursuant to a shareholder rights plan adopted in 2007, each outstanding share of our common stock carries with it a Right to purchase one share at a price of $140 per share. The Rights become exercisable (and separate from the shares) when certain specified events occur, including the acquisition of 15% or more of the common stock by a person or group (an "Acquiring Person") or the commencement of a tender or exchange offer for 15% or more of the common stock. In the event that an Acquiring Person acquires 15% or more of the common stock, or if we are the surviving corporation in a merger involving an Acquiring Person or if the Acquiring Person engages in certain types of self-dealing transactions, each Right entitles the holder to purchase for $140 per share (or the then-current exercise price), shares of our common stock having a market value of $280 (or two times the exercise price), subject to certain exceptions. Similarly, if we are acquired in a merger or other business combination or 50% or more of our assets or earning power is sold, each Right entitles the holder to purchase at the then-current exercise price that number of shares of common stock of the surviving corporation having a market value of two times the exercise price. The Rights do not entitle the holder thereof to vote or to receive dividends. The Rights will expire on August 6, 2017, and may be redeemed by us for $.01 per Right under certain circumstances.

Income Taxes

Income Taxes	12 Months Ended
	May 31, 2017
Income Taxes
Income Taxes	6. Income Taxes The provision for income tax (benefit) on income before taxes (benefit) includes the following components: For the Year Ended 2017 2016 2015 Current: Federal $ $ $ State Foreign ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The provision for income taxes on pre-tax income differs from the amount computed by applying the U.S. federal statutory income tax rate of 35% for fiscal 2017, 2016, and 2015 to income before taxes (benefit), due to the following: For the Year Ended 2017 2016 2015 Provision for income tax (benefit) at the federal statutory rate $ $ $ ) State income taxes, net of federal benefit and refunds Federal adjustments State net operating losses ) ) ) Valuation allowance for state deferred tax assets Prior period adjustments — ) — Effective settlement of prior tax position ) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Provision for income tax (benefit) $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ During the third quarter of fiscal 2016, we completed a reconciliation of our tax basis assets and liabilities and an analysis of our income tax payable which identified prior year immaterial errors netting to $0.2 million with $1.5 million recognized as income tax expense in discontinued operations and $1.3 million recognized as income tax benefit within income from continuing operations. Income (Loss) before provision for income tax (benefit) includes the following components: For the Year Ended 2017 2016 2015 Domestic $ $ $ ) Foreign ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities and assets result primarily from the differences in the timing of the recognition of transactions for financial reporting and income tax purposes. Our deferred tax liabilities and assets consist of the following components: May 31, 2017 2016 Deferred tax assets: Inventory costs $ $ Impairments Advanced billings Postretirement benefits Employee benefits State NOLs, tax credits and incentives Other ​ ​ ​ ​ ​ ​ ​ ​ Total deferred tax assets Valuation allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total deferred tax assets net of valuation allowance ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: Tangible and intangible assets ) ) Other ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total deferred tax liabilities ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax liabilities $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of May 31, 2017, we have determined that the realization of our deferred tax assets is more likely than not and that a valuation allowance is not required except for certain state deferred tax assets, net operating losses and credits. The change in the valuation allowance was primarily the result of state net operating losses in subsidiaries that are not expected to be utilized. The net operating losses have carry forward periods that range from 5 to 20 years. Our history of operating earnings, our expectations for continued future earnings, the nature of certain of our deferred tax assets and the scheduled reversal of deferred tax liabilities, primarily related to depreciation, support the recoverability of the majority of the deferred tax assets. Income tax payable at May 31, 2017 and 2016 was $12.3 million and $1.1 million, respectively and is included in Accrued Liabilities on the Consolidated Balance Sheets. A reconciliation of the beginning and ending amounts of unrecognized tax benefits was as follows: For the Year Ended 2017 2016 2015 Balance, beginning of year $ $ $ Additions for tax positions of prior years — Effective settlement of prior tax position ) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance, end of year $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In fiscal 2017, the reserve for unrecognized tax benefits decreased primarily as a result of effective settlement of tax positions for prior tax years which occurred upon the settlement of an IRS examination. Income tax expense in fiscal 2017 included a benefit of $2.2 million and discontinued operations included a benefit of $6.7 million for these effective settlements. All of our unrecognized tax benefits as of May 31, 2017 and 2016 would be recorded as a component of income tax expense or income from discontinued operations, if recognized. We accrue interest and penalties related to unrecognized tax benefits as a component of income tax expense. Fiscal years 2015 and subsequent are open for examination. Various states and foreign jurisdictions also remain open subject to their applicable statute of limitations.

Earnings Per Share

Earnings Per Share	12 Months Ended
	May 31, 2017
Earnings Per Share
Earnings Per Share	7. Earnings Per Share The computation of basic earnings per share is based on the weighted average number of common shares outstanding during each period. The computation of diluted earnings per share is based on the weighted average number of common shares outstanding during the period plus, when their effect is dilutive, incremental shares consisting of shares subject to stock options, shares issuable upon vesting of restricted stock awards and shares to be issued upon conversion of convertible debt. In accordance with ASC 260-10-45, Share-Based Payment Arrangements and Participating Securities and the Two-Class Method , our unvested restricted stock awards are deemed participating securities since these shares are entitled to participate in dividends declared on common shares. During periods of net income, the calculation of earnings per share for common stock excludes income attributable to unvested restricted stock awards from the numerator and excludes the dilutive impact of those shares from the denominator. During periods of net loss, no effect is given to the participating securities because they do not share in the losses of the Company. The following tables provide a reconciliation of the computations of basic and diluted earnings per share information for each of the years in the three-year period ended May 31, 2017 (shares in millions). For the Year Ended 2017 2016 2015 Basic and Diluted EPS: Income (Loss) from continuing operations $ $ $ ) Less income attributable to participating shares ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income (Loss) from continuing operations attributable to common shareholders ) Income from discontinued operations attributable to common shareholders ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income attributable to common shareholders for earnings per share $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares outstanding—basic Additional shares from assumed exercise of stock options ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares outstanding—diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share—basic: Earnings (Loss) from continuing operations $ $ $ ) Earnings from discontinued operations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share—basic $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share—diluted: Earnings (Loss) from continuing operations $ $ $ ) Earnings from discontinued operations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share—diluted $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At May 31, 2017, 2016 and 2015, respectively, outstanding options to purchase 11,200 shares, 1,374,200 shares, and 168,200 shares of common stock were not included in the computation of diluted earnings per share, because the exercise price of these options was greater than the average market price of the common shares for the period then ended.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	May 31, 2017
Employee Benefit Plans
Employee Benefit Plans	8. Employee Benefit Plans Defined Benefit Plans Prior to January 1, 2000, the pension plan for domestic salaried and non-union hourly employees had a benefit formula based primarily on years of service and compensation. Effective January 1, 2000, we converted our defined benefit plan for substantially all domestic salaried and certain hourly employees to a cash balance pension plan. Under the cash balance pension plan, the retirement benefit is expressed as a dollar amount in an account that grows with annual pay-based credits and interest on the account balance. The interest crediting rate under our cash balance plan is determined quarterly and is equal to 100% of the average 30-year treasury rate for the second month preceding the applicable quarter published by the Internal Revenue Service. The average interest crediting rate under our cash balance plan for the fiscal year ended May 31, 2017 was 4.5%. Effective June 1, 2005, the existing cash balance plan was frozen and the annual pay-based credits were discontinued. Also effective June 1, 2005, the defined contribution plan was modified to include increased employer contributions and an enhanced profit sharing formula. Defined pension benefits for certain union hourly employees are based primarily on a fixed amount per year of service. We also have a defined benefit pension plan covering certain employees in the Netherlands. Benefit formulas are based generally on years of service and compensation. We provide eligible outside directors with benefits upon retirement on or after age 65 provided they have completed at least five years of service as a director. Benefits are paid quarterly in cash equal to 25% of the annual retainer fee payable to active outside directors. Payment of benefits commences upon retirement and continues for a period equal to the total number of years of the retired director's service up to a maximum of ten years, or death, whichever occurs first. In fiscal 2001, we terminated this plan for any new members of the Board of Directors first elected after May 31, 2001. No current directors participate in this plan. The change to our projected benefit obligation and the fair value of our plan assets for our pension plans in the United States and other countries was as follows: May 31, 2017 2016 Change in projected benefit obligation: Projected benefit obligation at beginning of year $ $ Service cost Interest cost Participant contributions Net actuarial gain ) ) Benefit payments ) ) Foreign currency translation adjustment ​ ​ ​ ​ ​ ​ ​ ​ Projected benefit obligation at end of year $ $ ​ ​ ​ ​ ​ ​ ​ ​ Change in the fair value of plan assets: Fair value of plan assets at beginning of year $ $ Actual return on plan assets ) Employer contributions Participant contributions Benefit payments ) ) Foreign currency translation adjustment ​ ​ ​ ​ ​ ​ ​ ​ Fair value of plan assets at end of year $ $ ​ ​ ​ ​ ​ ​ ​ ​ Funded status at end of year $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amounts recognized in the Consolidated Balance Sheets consisted of the following: May 31, 2017 2016 Accrued liabilities $ ) $ ) Other liabilities and deferred income ) ) ​ ​ ​ ​ ​ ​ ​ ​ Funded status at end of year $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amounts recognized in accumulated other comprehensive loss at May 31, 2017 and 2016, respectively, consisted of the following: May 31, 2017 2016 Actuarial loss $ $ Prior service credit ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For all of our pension plans, both the projected benefit obligation and the accumulated benefit obligation are in excess of the individual plans' assets. The accumulated benefit obligation for all pension plans was $140.0 million as of both May 31, 2017 and 2016. Net Periodic Benefit Cost Pension expense charged to the Consolidated Statements of Income includes the following components: For the Year Ended 2017 2016 2015 Service cost $ $ $ Interest cost Expected return on plan assets ) ) ) Curtailment — — Amortization of prior service cost — Recognized net actuarial loss ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The estimated amounts to be amortized from accumulated other comprehensive loss into expense during fiscal 2018 are as follows: Net actuarial loss $ Prior service cost — ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assumptions The assumptions used in accounting for our plans are estimates of factors including, among other things, the amount and timing of future benefit payments. The following table presents the key weighted-average assumptions used in the measurement of our projected benefit obligations: May 31, 2017 2016 Discount rate: Domestic plans % % International plan Rate of compensation increase: Domestic plans % % International plan A summary of the weighted-average assumptions used to determine net periodic pension expense is as follows: For the Year 2017 2016 2015 Discount rate: Domestic plans % % % International plan Rate of compensation increase: Domestic plans % % % International plan Expected long-term rate on plan assets: Domestic plans % % % International plan The discount rate was determined by projecting the expected future benefit payments as defined for the projected benefit obligation, discounting those expected payments using a theoretical zero-coupon spot yield curve derived from a universe of high-quality bonds as of the measurement date, and solving for the single equivalent discount rate that resulted in the same projected benefit obligation. Plan Assets The following table sets forth the actual asset allocation and target allocations for our U.S. pension plans: May 31, Target Asset 2017 2016 Equity securities % % 45 - 75 % Fixed income securities 15 - 25 % Other 0 - 25 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ % % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The assets of U.S pension plans are invested in compliance with the Employee Retirement Income Security Act of 1974. The investment goals are to provide a total return that, over the long term, optimizes the long-term return on plan assets at an acceptable risk, and to maintain a broad diversification across asset classes and among investment managers. We believe that there are no significant concentrations of risk within our plan assets as of May 31, 2017. The use of derivatives for the purpose of speculation are not permitted. The assets of the U.S. pension plans are invested primarily in equity and fixed income mutual funds, individual common stocks, and fund-of-funds hedge funds. The assets of the non-domestic plan are invested in funds-of-funds where each fund holds a portfolio of equity and fixed income mutual funds. To develop our expected long-term rate of return assumption on domestic plans, we use long-term historical return information for our targeted asset mix and current market conditions. The expected return for each asset class is weighted based on the target asset allocation to develop the expected long-term rate of return on plan assets assumption. While consideration is given to recent performance, the assumption represents a long-term, prospective rate of return. The following table sets forth by level, within the fair value hierarchy, pension plan assets at their fair value as of May 31, 2017: Level 1 1 Level 2 2 Level 3 3 Total Equity securities: U.S. mutual funds $ $ — $ — $ International mutual funds — — Fixed income: Government securities and corporate bond mutual funds — — Funds-of-funds — Hedge funds — — Cash and cash equivalents — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investments $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following table sets forth by level, within the fair value hierarchy, pension plan assets at their fair value as of May 31, 2016: Level 1 1 Level 2 2 Level 3 3 Total Equity securities: U.S. common stock $ $ — $ — $ U.S. mutual funds — — International common stock — — International mutual funds — — Fixed income: Government securities and corporate bond mutual funds — — Funds-of-funds — Hedge funds — — Cash and cash equivalents — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investments $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 1 Quoted prices in active markets for identical assets that we have the ability to access as of the reporting date. 2 Inputs other than quoted prices included within Level 1 that are directly observable for the asset or indirectly observable through corroboration with observable market data. 3 Unobservable inputs, such as internally developed pricing models or third party valuations for the asset due to little or no market activity for the asset. The following table presents the reconciliation of Level 3 pension assets measured at fair value for the fiscal years ended May 31, 2017 and 2016: Hedge Funds Fund-of-funds Total Balance as of May 31, 2015 $ $ $ Return on plan assets related to assets still held at May 31, 2016 ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2016 Sales — ) ) Return on plan assets related to assets still held at May 31, 2017 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2017 $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Valuation Techniques Used to Determine Fair Value Cash equivalents are investments with maturities of three months or less when purchased. The fair values are based on observable market prices and categorized as Level 1. With respect to individually held equity securities, including investments in U.S. and international securities, the trustees obtain prices from pricing services, whose prices are obtained from direct feeds from market exchanges, which we are able to independently corroborate. Equity securities held individually are primarily traded on exchanges that contain only actively traded securities, due to the volume trading requirements imposed by these exchanges. Equity securities are valued based on quoted prices in active markets and categorized as Level 1. Equity and fixed income mutual funds are maintained by investment companies that hold certain investments in accordance with a stated set of fund objectives, which are consistent with our overall investment strategy. The values of some of these funds are publicly quoted. For equity and fixed income mutual funds which are publicly quoted, the funds are valued based on quoted prices in active markets and have been categorized as Level 1. As our funds-of-funds investments are also derived from quoted prices in active markets, we have categorized the funds-of-funds investments as Level 2. Hedge fund investments include those seeking to maximize absolute returns using a broad range of strategies to enhance returns and provide additional diversification. The fair value of hedge funds is determined using net asset value or its equivalent subject to certain restrictions, such as a lock-up period. As we may be limited in our ability to redeem the investments at the measurement date or within a reasonable period of time, the hedge fund investments are categorized as Level 3. Future Benefit Payments and Funding The following table summarizes our estimated future pension payments by fiscal year: Fiscal Year 2018 2019 2020 2021 2022 2023 to Estimated future pension payments $ $ $ $ $ $ Our contribution policy for the domestic plans is to contribute annually, at a minimum, an amount which is deductible for federal income tax purposes and that is sufficient to meet actuarially computed pension benefits. For our Netherlands pension plan, our policy is to fund at least the minimum amount required by the local laws and regulations. We anticipate contributing approximately $9.5 million to our pension plans during fiscal 2018. Postretirement Benefits Other Than Pensions We provide health and life insurance benefits for certain eligible retirees. The postretirement plan is unfunded and in fiscal 1995, we completed termination of postretirement health and life insurance benefits attributable to future services of collective bargaining and other domestic employees. The unfunded projected benefit obligation for this plan was $0.7 million and $0.9 million as of May 31, 2017 and 2016, respectively. We have omitted substantially all of the required disclosures related to this plan because the plan is not material to our consolidated financial position or results of operations. Defined Contribution Plan The defined contribution plan is a profit sharing plan that is intended to qualify as a 401(k) plan under the Internal Revenue Code. Under the plan, employees may contribute up to 75% of their pretax compensation, subject to applicable regulatory limits. We may make matching contributions up to 5% of compensation as well as discretionary profit sharing contributions. Our contributions vest on a pro-rata basis during the first three years of employment. We also provide profit sharing benefits for certain executives and key employees to supplement the benefits provided by the defined contribution plan. Expense charged to the Consolidated Statements of Income for our matching contributions, including profit sharing contributions, was $12.7 million in fiscal 2017, $11.2 million in fiscal 2016 and $12.1 million in fiscal 2015 for these plans.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	May 31, 2017
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Loss	9. Accumulated Other Comprehensive Loss Changes in our accumulated other comprehensive loss ("AOCL") by component for each of the years in the three-year period ended May 31, 2017 were as follows: Currency Pension Derivative Total Balance as of June 1, 2014 $ $ ) $ ) $ ) Other comprehensive income (loss) before reclassifications ) ) ) Sale of Telair Cargo Group — Amounts reclassified from AOCL — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive income (loss) ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2015 ) — ) Reclassifications within AOCL ) — — Other comprehensive income (loss) before reclassifications — ) — ) Amounts reclassified from AOCL — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive loss — ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2016 ) ) — ) Other comprehensive loss before reclassifications ) — Amounts reclassified from AOCL — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive income (loss) ) — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2017 $ ) $ ) $ — $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Aircraft Portfolio

Aircraft Portfolio	12 Months Ended
	May 31, 2017
Aircraft Portfolio
Aircraft Portfolio	10. Aircraft Portfolio Aircraft Owned with Joint Venture Partners We have ownership interests in two aircraft with joint venture partners at May 31, 2017 which are available for lease or sale to commercial air carriers. Our equity investment was approximately $10.7 million and $15.0 million as of May 31, 2017 and 2016, respectively, and is included in Other noncurrent assets on the Consolidated Balance Sheet. Our aircraft joint ventures primarily include investments in limited liability companies that are accounted for under the equity method of accounting. For our aircraft joint ventures accounted for under the equity method of accounting, our membership interest is 50%, and the primary business of these joint ventures is the acquisition, ownership, lease and disposition of certain commercial aircraft. Aircraft were purchased with cash contributions by the members of the joint ventures and debt financing provided on a limited recourse basis. Under the terms of servicing agreements with certain of the joint ventures, we provide administrative services and technical advisory services, including aircraft evaluations, oversight and logistical support of the maintenance process and records management. We also provide evaluation and inspection services prior to the purchase of an aircraft and remarketing services with respect to the divestiture of aircraft by the joint ventures. During fiscal 2017, 2016 and 2015, we were paid $1.2 million, $0.9 million and $0.1 million, respectively, for such services. The income tax benefit or expense related to the operations of the joint ventures is recorded by the member companies. Distributions from joint ventures are classified as operating or investing activities in the Consolidated Statements of Cash Flows based upon an evaluation of the specific facts and circumstances of each distribution. Wholly-Owned Aircraft In addition to the commercial aircraft owned with joint venture partners, we also previously owned 100% of two aircraft which we sold in the fourth quarter of fiscal 2015 for $11.0 million. The carrying value of these two aircraft was $25.8 million which resulted in the recognition of a loss on sale of $14.8 million.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	May 31, 2017
Commitments and Contingencies
Commitments and Contingencies	11. Commitments and Contingencies On October 3, 2003, we entered into a sale-leaseback transaction whereby we sold and leased back a facility located in Garden City, New York. The lease is classified as an operating lease. Net proceeds from the sale of the facility were $14.0 million and the cost and related accumulated depreciation of the facility of $9.5 million and $4.6 million, respectively, were removed from the Consolidated Balance Sheet at the time of sale. The gain realized on the sale of $9.1 million has been deferred and is being amortized over the 20-year lease term. As of May 31, 2017 and 2016, the unamortized balance of the deferred gain was approximately $2.9 million and $3.4 million, respectively, and is included in Other liabilities and deferred income on the Consolidated Balance Sheet. During the fourth quarter of fiscal 2015, we entered into a sale-leaseback transaction for our two S-92 rotary-wing aircraft resulting in the recognition of a loss of $1.1 million. We received sales proceeds of $40.3 million in fiscal 2015 which were deferred as a sale-leaseback advance pending completion of the sale transactions. Both of the S-92 aircraft sales were completed in fiscal 2016 and the related leases ended in fiscal 2017. During fiscal 2016, we received proceeds of $38.5 million from sale-leaseback transactions for two AW-189 rotary-wing aircraft which are supporting search and rescue operations in the Falkland Islands. The $1.7 million gain realized on the sale was deferred and is being amortized over the lease term of ten years. In addition to the leases described above, we lease other facilities and equipment under agreements that are classified as operating leases that expire at various dates through 2034. Future minimum payments under all operating leases at May 31, 2017 are as follows: 2018 $ 2019 2020 2021 2022 2023 and thereafter Rental expense for facilities and equipment during fiscal years 2017, 2016, and 2015 was $31.9 million, $33.5 million, and $33.7 million, respectively. We enter into purchase obligations which arise in the ordinary course of business and represent a binding commitment to acquire inventory, including raw materials, parts and components, as well as equipment to support the operations of our business. The aggregate amount of purchase obligations due in each of the next five fiscal years is $231.2 million in 2018, $37.7 million in 2019, $1.4 million in 2020, $2.7 million in 2021 and none in 2022. We routinely issue letters of credit and performance bonds in the ordinary course of our business. These instruments are typically issued in conjunction with insurance contracts or other business requirements. The total of these instruments outstanding at May 31, 2017 was approximately $13.6 million. We are involved in various claims and legal actions, including environmental matters, arising in the ordinary course of business. In the opinion of management, the ultimate disposition of these matters will not have a material adverse effect on our consolidated financial condition or results of operations.

Other Noncurrent Assets

Other Noncurrent Assets	12 Months Ended
	May 31, 2017
Other Noncurrent Assets
Other Noncurrent Assets	12. Other Noncurrent Assets At May 31, 2017 and 2016, other noncurrent assets consisted of the following: May 31, 2017 2016 Assets under deferred compensation plan $ $ Costs in excess of billings Cash surrender value of life insurance Investments in joint ventures License fees Other ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ License Fees In June 2011, we entered into a ten-year agreement with Unison Industries to be the exclusive worldwide aftermarket distributor for Unison's electrical components, sensors, switches and other systems for aircraft and industrial uses. In connection with the agreement, we agreed to pay Unison Industries $20.0 million for the exclusive distribution rights with $7.0 million paid in June 2011 and $1.3 million payable by January 31 of each calendar year beginning in January 2012 through 2021. As of May 31, 2017 and 2016, the unamortized balance of the license is $7.2 million and $8.8 million, respectively, and is being amortized over a ten-year period. The current portion of the deferred payments of $1.3 million is recorded in Accrued liabilities and the long-term portion of $3.2 million is included in Other liabilities and deferred income on the Consolidated Balance Sheet.

Acquisitions

Acquisitions	12 Months Ended
	May 31, 2017
Acquisitions
Acquisitions	13. Acquisitions On April 10, 2017, we acquired the trading business of ACLAS Global Limited ("ACLAS"). In conjunction with the acquisition, we entered into a multi-year component support and repair contract covering approximately 100 of ACLAS' aircraft. The purchase price of the acquisition was $12.0 million paid at closing with $3.0 million in deferred consideration payable over the next three years. This business operates as part of our Aviation Services segment. The amounts recorded for certain assets are preliminary in nature and are subject to adjustment as additional information is obtained about their acquisition date fair value. The final determination of the fair values will be completed within the one year measurement period. The preliminary fair value of assets acquired is as follows: Inventory $ Equipment on or available for long-term lease Intangible assets ​ ​ ​ ​ ​ Assets acquired $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ On December 4, 2015, we acquired certain assets of Vantem Modular LLC, which designs, manufactures, and distributes modular shelters. The purchase price of the acquisition was $4.8 million paid at closing with future royalties of up to $5.0 million. This business operates as part of our Expeditionary Services segment. The fair value of net assets acquired is as follows: Current assets $ Equipment Intangible assets Contingent consideration ) ​ ​ ​ ​ ​ Net assets acquired Goodwill ​ ​ ​ ​ ​ Purchase price $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Business Segment Information

Business Segment Information	12 Months Ended
	May 31, 2017
Business Segment Information
Business Segment Information	14. Business Segment Information Segment Reporting Consistent with how our chief operating decision making officer (Chief Executive Officer) evaluates performance and the way we are organized internally, we report our activities in two segments: Aviation Services comprised of supply chain and MRO activities and Expeditionary Services comprised of airlift and mobility activities. The Aviation Services segment consists of aftermarket support and services businesses that provide spares and maintenance support for aircraft operated by our commercial and government/defense customers. Sales in the Aviation Services segment are derived from the sale and lease of a wide variety of new, overhauled and repaired engine and airframe parts and components to the commercial aviation and government and defense markets. We provide customized inventory supply chain management, performance based logistics programs, aircraft component repair management services, and aircraft modifications. The segment also includes repair, maintenance and overhaul of aircraft, landing gear and components. Cost of sales consists principally of the cost of product, direct labor, and overhead. The Expeditionary Services segment consists of businesses that provide products and services supporting the movement of equipment and personnel by the U.S. DoD, foreign governments and non-governmental organizations. Sales in the Expeditionary Services segment are derived from the delivery of airlift services to mostly government and defense customers and the design and manufacture of pallets, shelters, and containers used to support the U.S. military's requirements for a mobile and agile force. We also provide engineering, design, and system integration services for specialized command and control systems and design and manufacture advanced composite materials for commercial, business and military aircraft. Cost of sales consists principally of aircraft maintenance costs, depreciation, the cost of material to manufacture products, direct labor and overhead. The accounting policies for the segments are the same as those described in Note 1. Our chief operating decision making officer (Chief Executive Officer) evaluates performance based on the reportable segments and utilizes gross profit as a primary profitability measure. Gross profit is calculated by subtracting cost of sales from sales. The assets and certain expenses related to corporate activities are not allocated to the segments. Our reportable segments are aligned principally around differences in products and services. Selected financial information for each segment is as follows: For the Year Ended May 31, 2017 2016 2015 Net sales: Aviation Services $ $ $ Expeditionary Services ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended May 31, 2017 2016 2015 Gross profit (loss): Aviation Services $ $ $ Expeditionary Services ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ May 31, 2017 2016 2015 Total assets: Aviation Services $ $ $ Expeditionary Services Corporate and discontinued operations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended May 31, 2017 2016 2015 Capital expenditures: Aviation Services $ $ $ Expeditionary Services Corporate ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total continuing operations Discontinued operations — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended May 31, 2017 2016 2015 Depreciation and amortization: 1 Aviation Services $ $ $ Expeditionary Services Corporate ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total continuing operations Discontinued operations — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 1 Includes depreciation and amortization of stock-based compensation. The following table reconciles segment gross profit to income (loss) from continuing operations before provision for income taxes. For the Year Ended May 31, 2017 2016 2015 Segment gross profit $ $ $ Selling, general and administrative ) ) ) Earnings (Loss) from joint ventures ) ) Loss on extinguishment of debt — ) ) Interest expense ) ) ) Interest income ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income (Loss) from continuing operations before provision for income taxes $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The U.S. Department of Defense, other U.S. government agencies and their contractors are our only customers representing 10% or more of total sales in any of the last three fiscal years. Sales by segment for these customers are as follows: For the Year Ended May 31, 2017 2016 2015 Aviation Services $ $ $ Expeditionary Services ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Percentage of total sales % % % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales by type of product/service was as follows: For the Year Ended May 31, 2017 2016 2015 Aviation supply chain $ $ $ Maintenance, repair and overhaul services Expeditionary airlift services Mobility products ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Geographic Data May 31, 2017 2016 Long-lived assets: United States $ $ Europe Other ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Sales to unaffiliated customers in foreign countries (including sales through foreign sales offices of domestic subsidiaries) were approximately $618.8 million (35.0% of total sales), $494.6 million (29.1% of total sales) and $538.9 million (33.2% of total sales) in fiscal 2017, 2016 and 2015, respectively.

Legal Proceedings

Legal Proceedings	12 Months Ended
	May 31, 2017
Legal Proceedings
Legal Proceedings	15. Legal Proceedings We are not a party to any material pending legal proceeding (including any governmental or environmental proceeding) other than routine litigation incidental to our business except for the following: DynCorp International LLC v. AAR Airlift Group, Inc. On September 5, 2015, DynCorp International LLC ("DynCorp") filed a complaint in the United States District Court for the Middle District of Florida, Orlando Division (the "District Court"), accusing AAR Airlift Group, Inc. ("AAR Airlift"), a wholly-owned subsidiary of AAR CORP., of misappropriation of DynCorp information, including trade secrets, and other related allegations. DynCorp's complaint, which sought damages in an unspecified amount and a preliminary injunction, alleged that AAR Airlift engaged in this conduct in connection with the submission of proposals in response to the solicitation issued by the U.S. Department of State ("DOS") Bureau of International Narcotics and Law Enforcement Affairs, Office of Aviation ("INL/A") in support of the Global Aviation Support Services program. The INL/A contract was subsequently awarded to AAR Airlift on September 1, 2016 as described below under "Court of Federal Claims INL/A Proceeding". The District Court denied DynCorp's preliminary injunction motion, and on October 19, 2015, DynCorp filed an amended complaint with the District Court. On January 14, 2016, the District Court granted AAR Airlift's motion to dismiss DynCorp's amended complaint. On February 2, 2016, DynCorp appealed the District Court's order to the United States Court of Appeals for the Eleventh Circuit (the "Eleventh Circuit"). On November 21, 2016, the Eleventh Circuit reversed in part the District Court's dismissal of the amended complaint and remanded the case to the District Court for further proceedings. The District Court set a discovery schedule that ends September 1, 2017 and a trial date of April 2, 2018. On June 16, 2017, the District Court granted AAR Airlift's motion to stay the legal proceeding against AAR Airlift. The stay will remain in effect until the earlier of (a) November 1, 2017 or (b) the entry of a decision of the United Stated Court of Federal Claims ("COFC"), on DynCorp's protest of the award of the INL/A contract to AAR Airlift. The District Court's stay immediately halted all discovery and other activity in the DynCorp lawsuit. AAR Airlift will continue to defend itself vigorously against DynCorp's lawsuit, which it believes is entirely without merit.

Selected Quarterly Data (Unaudi

Selected Quarterly Data (Unaudited)	12 Months Ended
	May 31, 2017
Selected Quarterly Data (Unaudited)
Selected Quarterly Data (Unaudited)	16. Selected Quarterly Data (Unaudited) The unaudited selected quarterly data for fiscal years ended May 31, 2017 and 2016 is as follows: Fiscal 2017 First Second Third Fourth Full Sales $ $ $ $ $ Gross profit Income from continuing operations Income (Loss) from discontinued operations ) — Net income Earnings (Loss) per share—basic: (1) Continuing operations Discontinued operations ) — Earnings per share—basic Earnings (Loss) per share—diluted: (1) Continuing operations Discontinued operations ) — Earnings per share—diluted Fiscal 2016 First Second Third Fourth Full Sales $ $ $ $ $ Gross profit Income from continuing operations Income (Loss) from discontinued operations (2) ) ) Net income Earnings (Loss) per share—basic: (1) Continuing operations Discontinued operations ) ) — Earnings per share—basic Earnings (Loss) per share—diluted: (1) Continuing operations Discontinued operations ) ) — Earnings per share—diluted 1 The earnings-per-share computation for the year is a separate, annual calculation. Accordingly, the sum of the quarterly earnings-per-share amounts does not necessarily equal the earnings per share for the year. 2 First quarter income from discontinued operations in fiscal 2016 reflects a pre-tax gain of $27.7 million for the receipt of contingent consideration from the sale of Telair Cargo Group in fiscal 2015.

Allowance for Doubtful Accounts

Allowance for Doubtful Accounts	12 Months Ended
	May 31, 2017
Allowance for Doubtful Accounts
Allowance for Doubtful Accounts	17. Allowance for Doubtful Accounts May 31, 2017 2016 2015 Balance, beginning of year $ $ $ Provision charged to operations Deductions for accounts written off, net of recoveries ) ) ) Sale of Telair Cargo Group — — ) Reclassification to assets of discontinued operations — — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance, end of year $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	May 31, 2017
Summary of Significant Accounting Policies
Principles of Consolidation	Principles of Consolidation The accompanying Consolidated Financial Statements include the accounts of the Company and its majority-owned subsidiaries after elimination of intercompany accounts and transactions. The equity method of accounting is used for investments in other companies in which we have significant influence; generally this represents common stock ownership of at least 20% and not more than 50% (see Note 10 for a discussion of aircraft joint ventures).
Revenue Recognition	Revenue Recognition Sales and related cost of sales for product sales are recognized upon shipment of the product to the customer. Our standard terms and conditions provide that title passes to the customer when the product is shipped to the customer. Sales of certain defense products are recognized upon customer acceptance, which includes transfer of title. Under the majority of our expeditionary airlift services contracts, we are paid and record as revenue a fixed daily amount per aircraft for each day an aircraft is available to perform airlift services. In addition, we are paid and record as revenue an amount which is based on number of hours flown. Sales from services and the related cost of services are generally recognized when customer-owned material is shipped back to the customer. We have adopted this accounting policy because at the time the customer-owned material is shipped back to the customer; all services related to that material are complete as our service agreements generally do not require us to provide services at customer sites. Furthermore, serviced units are typically shipped to the customer immediately upon completion of the related services. Sales and related cost of sales for certain large airframe maintenance contracts and performance-based logistics programs are recognized by the percentage of completion method, based on the relationship of costs incurred to date to the estimated total costs. When our experience and projections indicate adjustments to the estimated margin are required, changes are recognized using the cumulative catch-up method with the impact of the change from inception to date recorded in the current period. Net favorable cumulative catch-up adjustments recognized during fiscal 2017, 2016, and 2015 were $8.5 million, $3.7 million, and $2.5 million, respectively. Lease revenues are recognized as earned. Income from monthly or quarterly rental payments is recorded in the pertinent period according to the lease agreement. However, for leases that provide variable rents, we recognize lease income on a straight-line basis. In addition to a monthly lease rate, some engine leases require an additional rental amount based on the number of hours the engine is used in a particular month. Lease income associated with these contingent rentals is recorded in the period in which actual usage is reported to us by the lessee, which is normally the month following the actual usage. Certain supply chain management programs we provide to our customers contain multiple elements or deliverables, such as program and warehouse management, parts distribution, and maintenance and repair services. We recognize revenue for each element or deliverable that can be identified as a separate unit of accounting at the time of delivery based upon the relative fair value of the products and services. Included in accounts receivable as of May 31, 2017 and 2016, are $14.5 million and $29.8 million, respectively, of unbilled accounts receivable related to our KC-10 supply agreement. These unbilled accounts receivable relate to costs we have incurred on parts that were requested and accepted by our customer to support the program. These costs have not been billed by us because the customer has not issued the final paperwork necessary to allow for billing. In June 2016, the U.S. Air Force awarded the new contract for the KC-10 Extender Contractor Logistics Support Program ("KC-10 Program") to a competitor. Our principal services under the prior contract for the KC-10 Program were completed in January 2017; however, we expect limited services will continue for an unspecified period of time. Sales for the KC-10 Program during fiscal 2017, 2016 and 2015 were $110.6 million, $148.1 million, and $111.4 million, respectively. Gross profit for the KC-10 Program during fiscal 2017, 2016 and 2015 was $3.7 million, $12.0 million, and $4.5 million, respectively.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts We maintain an allowance for doubtful accounts to reflect the expected uncollectibility of accounts receivable based on past collection history and specific risks identified among uncollected accounts. In determining the required allowance, we consider factors such as general and industry-specific economic conditions, customer credit history, and our customers' current and expected future financial performance. The majority of our customers are recurring customers with an established payment history. Certain customers are required to undergo an extensive credit check prior to delivery of products or services.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets In accordance with Accounting Standards Codification ("ASC") 350, Intangibles—Goodwill and Other , goodwill and other intangible assets deemed to have indefinite lives are not amortized, but are subject to annual impairment tests. We review and evaluate our goodwill and indefinite life intangible assets for potential impairment at a minimum annually, on May 31, or more frequently if circumstances indicate that impairment is possible. We utilize both the qualitative approach and the two-step quantitative approach to evaluate goodwill for impairment. In the first step of the quantitative approach, we compare the fair value of the reporting unit with its carrying value, including goodwill. If the estimated fair value of the reporting unit is less than its carrying value, we would be required to complete a second step to determine the amount of goodwill impairment. The second step of the test requires the allocation of the reporting unit's fair value to its assets and liabilities, including any unrecognized intangible assets, in a hypothetical analysis that calculates the implied fair value of goodwill as if the reporting unit was being acquired in a business combination. If the implied fair value of goodwill is less than the carrying value, the difference is recorded as an impairment loss. As of May 31, 2017, we have five reporting units with only four of the reporting units assigned goodwill. Our four reporting units with goodwill include two in our Aviation Services segment (Aviation Supply Chain and Maintenance, Repair, and Overhaul) and two in our Expeditionary Services segment (Airlift and Mobility). We utilized the qualitative assessment approach for the two Aviation Services reporting units and the two-step quantitative approach for the two Expeditionary Services reporting units. We performed the annual qualitative analysis for the two Aviation Services reporting units and concluded it was more likely than not that the fair value of each reporting unit exceeded their carrying values, and thus no impairment charge was recorded. Step one of the quantitative goodwill impairment test was completed for the two Expeditionary Services reporting units and the estimated fair value for each reporting unit exceeded its carrying value. Accordingly, there was no indication of impairment and the second step was not performed. We estimate the fair value of each Expeditionary Services reporting unit using an income approach based on discounted cash flows. The assumptions we used to estimate the fair value of these reporting units are based on historical performance, as well as forecasts used in our current business plan, and require considerable management judgment. We use a discount rate based on our consolidated weighted average cost of capital which is adjusted for each of our reporting units based on their specific risk and size characteristics. The fair value measurements used for our goodwill impairment testing use significant unobservable inputs, which reflect our own assumptions about the inputs that market participants would use in measuring fair value. The fair value of our reporting units is also impacted by our overall market capitalization and may be impacted by volatility in our stock price and assumed control premium, among other items. Changes in the carrying amount of goodwill by segment for fiscal 2017 and 2016 are as follows: Aviation Expeditionary Total Balance as of May 31, 2015 $ $ $ Acquisition — Deferred tax adjustments ) — ) Foreign currency translation adjustments ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2016 Foreign currency translation adjustments ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2017 $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Intangible assets with finite useful lives are amortized on a straight-line basis over their estimated useful lives. Intangible assets, other than goodwill, are comprised of the following: May 31, 2017 Gross Accumulated Net Amortizable intangible assets: Customer relationships $ $ ) $ Developed technology ) Lease agreements ) FAA certificates ) Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ) Unamortized intangible assets: Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ May 31, 2016 Gross Accumulated Net Amortizable intangible assets: Customer relationships $ $ ) $ Developed technology ) Lease agreements ) FAA certificates ) Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ) Unamortized intangible assets: Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Customer relationships are being amortized over 10-20 years, developed technology is being amortized over 7-15 years, lease agreements are being amortized over 5-18 years, and the FAA certificates are being amortized over 20 years. Amortization expense recorded during fiscal 2017, 2016 and 2015 was $4.3 million, $4.4 million, and $4.6 million, respectively. The estimated aggregate amount of amortization expense for intangible assets in each of the next five fiscal years is $4.5 million in 2018, $3.8 million in 2019, $3.5 million in 2020, $3.5 million in 2021 and $2.7 million in 2022.
Foreign Currency	Foreign Currency Our foreign subsidiaries utilize the local currency as their functional currency. All balance sheet accounts of foreign subsidiaries transacting business in currencies other than the U.S. dollar are translated at year-end exchange rates. Revenues and expenses are translated at average exchange rates during the year. Translation adjustments are excluded from the results of operations and are recorded in stockholders' equity as a component of accumulated other comprehensive loss until such subsidiaries are liquidated.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of highly liquid instruments which have original maturities of three months or less when purchased.
Financial Instruments and Concentrations of Market or Credit Risk	Financial Instruments and Concentrations of Market or Credit Risk Financial instruments that potentially subject us to concentrations of market or credit risk consist principally of trade receivables. While our trade receivables are diverse and represent a number of entities and geographic regions, the majority are with the U.S. Department of Defense and its contractors and entities in the aviation industry. Accounts receivable due from the U.S. Department of Defense were $43.0 million and $43.7 million at May 31, 2017 and 2016, respectively. Additionally, included in accounts receivable as of May 31, 2017 and 2016, are $25.5 million and $42.4 million, respectively, of accounts receivable from a large defense contractor. We perform regular evaluations of customer payment experience, current financial condition, and risk analysis. We may require collateral in the form of security interests in assets, letters of credit, and/or obligation guarantees from financial institutions for transactions executed on other than normal trade terms. The carrying amounts of cash and cash equivalents, accounts receivable, and accounts and trade notes payable approximate fair value because of the short-term maturity of these instruments. The carrying value of long-term debt bearing a variable interest rate approximates fair value. Fair value estimates are made at a specific point in time based on relevant market information about the financial instrument. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. Changes in assumptions could significantly affect the estimates.
Inventories	Inventories Inventories are valued at the lower of cost or market (estimated net realizable value). Cost is determined by the specific identification, average cost, or first-in, first-out methods. From time-to-time, we purchase aircraft and engines for disassembly to individual parts and components. Costs are assigned to these individual parts and components utilizing list prices from original equipment manufacturers and recent sales history. The following is a summary of inventories: May 31, 2017 2016 Raw materials and parts $ $ Work-in-process Aircraft and engine parts, components and finished goods Aircraft held for sale and related support parts ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ We classify certain aircraft from our expeditionary airlift business as assets held for sale at the time management commits to a plan to sell the aircraft, changes to the planned sale are not likely, the aircraft are actively marketed and available for immediate sale, and the sale is expected to be completed within one year. Upon designation of an aircraft as held for sale, we record the aircraft's value at the lower of its carrying value or its estimated fair value, less estimated costs to sell. Assets held for sale are not depreciated. Aircraft may be classified as assets held for sale for more than one year as we continue to actively market the aircraft at reasonable prices. Certain aircraft types we currently have available for sale are specifically designed for particular functions which limits the marketability of those assets. During fiscal 2015, we recognized impairment charges of $8.9 million reflecting the decrease in fair value for certain aircraft held for sale and related rotable assets. During the fourth quarter of fiscal 2015, we entered into a sale-leaseback transaction for our two S-92 rotary-wing aircraft resulting in the recognition of a loss of $1.1 million. We received sales proceeds of $40.3 million in fiscal 2015 which were deferred as a sale-leaseback advance pending completion of the sale transactions. Both of the S-92 aircraft sales were completed in fiscal 2016 and the related leases ended in fiscal 2017.
Equipment under Leases	Equipment under Leases Lease revenue is recognized as earned. The cost of the asset under lease is the original purchase price plus overhaul costs. Depreciation for aircraft is computed using the straight-line method over the estimated service life of the equipment. The balance sheet classification of equipment under lease is generally based on lease term, with fixed-term leases less than twelve months generally classified as short-term and all others generally classified as long-term. Equipment on short-term lease includes aircraft engines and parts on or available for lease to satisfy customers' immediate short-term requirements. The leases are renewable with fixed terms, which generally vary from one to twelve months. In conjunction with our decision to exit certain product lines in our landing gear business, we recognized an impairment charge of $17.7 million related to rotable assets in fiscal 2015. Equipment on long-term lease consists of engines on lease with commercial airlines generally for more than twelve months and rotable parts used to support long-term supply chain programs. The rotable parts included in equipment on long-term lease are being depreciated on a straight-line basis over their estimated useful lives. During the fourth quarter of fiscal 2015, we sold our two remaining wholly-owned aircraft which were on long-term leases for $11.0 million which resulted in a loss on sale of $14.8 million. Future rent due to us under non-cancelable leases during each of the next five fiscal years is $31.6 million in 2018, $31.3 million in 2019, $31.2 million in 2020, $30.6 million in 2021, and $30.6 million in 2022.
Property, Plant and Equipment	Property, Plant and Equipment We record property, plant and equipment at cost. Depreciation is computed on the straight-line method over useful lives of 10-40 years for buildings and improvements and 3-10 years for equipment, furniture and fixtures, and capitalized software. Aircraft, major components in service, and associated rotable assets to support our expeditionary airlift services are depreciated over their estimated useful lives, which is generally 7-30 years. Leasehold improvements are amortized over the shorter of the estimated useful life or the term of the applicable lease. Repair and maintenance expenditures are expensed as incurred. Upon sale or disposal, cost and accumulated depreciation are removed from the accounts, and related gains and losses are included in results of operations. In accordance with ASC 360, Property, Plant and Equipment , we are required to test for impairment of long-lived assets whenever events or changes in circumstances indicate the carrying value of an asset may not be recoverable from its undiscounted cash flows. We utilize certain assumptions to estimate future undiscounted cash flows, including demand for our services, future market conditions and trends, business development pipeline of opportunities, current and future lease rates, lease terms, and residual values.
Income Taxes	Income Taxes We are subject to income taxes in the U.S., state, and several foreign jurisdictions. In the ordinary course of business, there can be transactions and calculations where the ultimate tax determination is uncertain. We recognize deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns in accordance with applicable accounting guidance for accounting for income taxes, using currently enacted tax rates in effect for the year in which the differences are expected to reverse. We record a valuation allowance when necessary to reduce deferred tax assets to the amount expected to be realized. Deferred tax assets are reduced by a valuation allowance if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. Both positive and negative evidence are considered in forming our judgment as to whether a valuation allowance is appropriate, and more weight is given to evidence that can be objectively verified. Valuation allowances are reassessed whenever there are changes in circumstances that may cause a change in judgment. The accounting for uncertainty in income taxes requires a more-likely-than-not threshold for financial statement recognition of tax positions taken or expected to be taken in a tax return. Where necessary, we record a liability for the difference between the benefit recognized for financial statement purposes and the tax position taken or expected to be taken on our tax return. To the extent that our assessment of such tax positions changes, the change in estimate is recorded in the period in which the determination is made.
Supplemental Information on Cash Flows	Supplemental Information on Cash Flows Supplemental information on cash flows is as follows: For the Year Ended 2017 2016 2015 Interest paid $ $ $ Income taxes paid Income tax refunds and interest received During fiscal 2017, treasury stock increased $12.2 million reflecting the repurchase of common shares of $19.8 million, restricted stock grants of $1.3 million and the re-issuance of shares upon exercise of stock options, net of shares withheld to satisfy statutory tax obligations, of $8.9 million. During fiscal 2016, treasury stock increased $21.3 million reflecting the repurchase of common shares of $18.8 million, restricted stock grants of $4.8 million and the re-issuance of shares upon exercise of stock options, net of shares withheld to satisfy statutory tax obligations, of $2.3 million. On May 29, 2015, we repurchased 4,185,960 shares of our common stock at a price of $31.90 per share pursuant to a tender offer utilizing $133.5 million cash on hand. Fees and expenses of $1.2 million were incurred related to the tender offer and were recorded in treasury stock. In addition to the tender offer, we also repurchased common shares of $16.8 million and re-issued shares upon exercise of stock options, net of shares withheld to satisfy statutory tax obligations, of $3.6 million during fiscal 2015.
Use of Estimates	Use of Estimates We have made estimates and utilized certain assumptions relating to the reporting of assets and liabilities and the disclosures of contingent liabilities to prepare these Consolidated Financial Statements in conformity with accounting principles generally accepted in the United States. Actual results could differ from those estimates.
New Accounting Pronouncements	New Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, which provides guidance for revenue recognition. This ASU affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of non-financial assets. This ASU will supersede the revenue recognition requirements in ASC 605, Revenue Recognition, and most industry-specific guidance. This ASU will also supersede certain cost guidance included in Subtopic 605-35, Revenue Recognition—Construction-Type and Production-Type Contracts. In August 2015, the FASB issued ASU No. 2015-14 which deferred the effective date of the new standard by one year which will make the new standard effective for us beginning June 1, 2018. The ASU may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of initial application. We continue to gain an understanding of the standard's revenue recognition model and are in the process of analyzing and documenting our significant customer contracts to evaluate the potential impact of the adoption of this new ASU. We have not yet selected a transition method for adoption nor determined the potential effect on our accounting policies and consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases. This ASU amends the existing accounting standards for lease accounting, including requiring lessees to recognize most leases on their balance sheets, including those classified as operating leases under the current accounting guidance. In addition, this ASU will require new qualitative and quantitative disclosures about the Company's leasing activities. This new standard will be effective for us beginning June 1, 2019 with early adoption permitted. This ASU requires a modified retrospective transition approach for all leases existing at, or entered into after, the date of initial application, with an option to use certain transition relief. We are in the preliminary phases of assessing the effect of this ASU on our portfolio of leases. While this assessment continues, we have not yet selected a transition date nor have we determined the effect of this ASU on our consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, "Improvements to Employee Share-Based Payment Accounting," which amends ASC Topic 718, Compensation—Stock Compensation. This ASU requires excess tax benefits or deficiencies for share-based payments be recorded in the period shares vest as income tax expense or benefit, rather than within Capital surplus . Cash flows related to excess tax benefits will be included in operating activities and will no longer be classified as a financing activity. This ASU will be effective for us beginning June 1, 2017 and no material impact on our financial statements is expected.

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	May 31, 2017
Summary of Significant Accounting Policies
Schedule of goodwill by reportable segment	Aviation Expeditionary Total Balance as of May 31, 2015 $ $ $ Acquisition — Deferred tax adjustments ) — ) Foreign currency translation adjustments ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2016 Foreign currency translation adjustments ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2017 $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of intangible assets, other than goodwill	May 31, 2017 Gross Accumulated Net Amortizable intangible assets: Customer relationships $ $ ) $ Developed technology ) Lease agreements ) FAA certificates ) Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ) Unamortized intangible assets: Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ May 31, 2016 Gross Accumulated Net Amortizable intangible assets: Customer relationships $ $ ) $ Developed technology ) Lease agreements ) FAA certificates ) Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ) Unamortized intangible assets: Trademarks — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of inventories	May 31, 2017 2016 Raw materials and parts $ $ Work-in-process Aircraft and engine parts, components and finished goods Aircraft held for sale and related support parts ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of supplemental information on cash flow	For the Year Ended 2017 2016 2015 Interest paid $ $ $ Income taxes paid Income tax refunds and interest received

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	May 31, 2017
Discontinued Operations
Schedule of income from discontinued operations	For the Year Ended 2017 2016 2015 Sales $ $ $ Cost of sales Selling, general and administrative expenses Interest expense, net. — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating income (loss) from discontinued operations ) ) Gain on sale of Telair Cargo Group — PSM Impairment charges — — ) Provision for income taxes (benefit) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income from discontinued operations Income attributable to noncontrolling interest — — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income from discontinued operations attributable to AAR $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Financing Arrangements (Tables)

Financing Arrangements (Tables)	12 Months Ended
	May 31, 2017
Financing Arrangements
Summary of carrying amount of debt	May 31, 2017 2016 Revolving Credit Facility expiring November 1, 2021 with interest payable monthly $ $ Industrial revenue bond (secured by property, plant and equipment) due August 1, 2018 with interest payable monthly Note payable due March 9, 2017 with floating interest rate, payable semi-annually on June 1 and December 1 — Capital lease obligations ​ ​ ​ ​ ​ ​ ​ ​ Total debt Current maturities of debt ) ) Debt issuance costs, net ) ) ​ ​ ​ ​ ​ ​ ​ ​ Long-term debt $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of borrowing activity under the Credit Agreement	For the Year Ended May 31, 2017 2016 2015 Maximum amount borrowed $ $ $ Average daily borrowings Average interest rate during the year % % %
Schedule of interest expense associated with the convertible notes	For the Year 2016 2015 Coupon interest $ $ Amortization of deferred financing fees Amortization of discount ​ ​ ​ ​ ​ ​ ​ ​ Interest expense related to convertible notes $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	May 31, 2017
Stock-Based Compensation
Schedule of assumptions used in the Black-Scholes option pricing model to estimate the fair value of stock option grant	Stock Options 2017 2016 Risk-free interest rate % % Expected volatility of common stock % % Dividend yield % % Expected option term in years
Summary of stock option activity	A summary of stock option activity for the three years ended May 31, 2017 consisted of the following (shares in thousands): 2017 2016 2015 Shares Weighted Shares Weighted Shares Weighted Outstanding at beginning of year $ $ $ Granted $ $ — $ — Exercised ) $ ) $ ) $ Cancelled ) $ ) $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at end of year $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options exercisable at end of year $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of additional information regarding stock options outstanding	The following table provides additional information regarding stock options outstanding as of May 31, 2017 (shares in thousands): Options Outstanding Options Exercisable Option Number Weighted-Average Weighted- Number Weighted- $12.00 - $20.00 $ $ $20.01 - $26.00 $ $ $26.01 - $34.50 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of restricted share activity	Restricted share activity during the fiscal year ended May 31, 2017 was as follows (shares in thousands): Number of Weighted Average Nonvested at May 31, 2016 $ Granted $ Vested ) $ Forfeited ) $ ​ ​ ​ ​ ​ ​ ​ ​ Nonvested at May 31, 2017 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	May 31, 2017
Income Taxes
Schedule of components of provision for income tax (benefit) on income before taxes (benefit)	For the Year Ended 2017 2016 2015 Current: Federal $ $ $ State Foreign ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of difference between the provision for income taxes on pre-tax income from the amount computed by applying the U.S. federal statutory tax rate	For the Year Ended 2017 2016 2015 Provision for income tax (benefit) at the federal statutory rate $ $ $ ) State income taxes, net of federal benefit and refunds Federal adjustments State net operating losses ) ) ) Valuation allowance for state deferred tax assets Prior period adjustments — ) — Effective settlement of prior tax position ) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Provision for income tax (benefit) $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of income (loss) before provision for income tax (benefit)	For the Year Ended 2017 2016 2015 Domestic $ $ $ ) Foreign ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of components of deferred tax liabilities and assets	May 31, 2017 2016 Deferred tax assets: Inventory costs $ $ Impairments Advanced billings Postretirement benefits Employee benefits State NOLs, tax credits and incentives Other ​ ​ ​ ​ ​ ​ ​ ​ Total deferred tax assets Valuation allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total deferred tax assets net of valuation allowance ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: Tangible and intangible assets ) ) Other ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total deferred tax liabilities ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax liabilities $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Reconciliation of unrecognized tax benefits	For the Year Ended 2017 2016 2015 Balance, beginning of year $ $ $ Additions for tax positions of prior years — Effective settlement of prior tax position ) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance, end of year $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	May 31, 2017
Earnings Per Share
Schedule of reconciliation of computations of basic and diluted earnings per share information	The following tables provide a reconciliation of the computations of basic and diluted earnings per share information for each of the years in the three-year period ended May 31, 2017 (shares in millions). For the Year Ended 2017 2016 2015 Basic and Diluted EPS: Income (Loss) from continuing operations $ $ $ ) Less income attributable to participating shares ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income (Loss) from continuing operations attributable to common shareholders ) Income from discontinued operations attributable to common shareholders ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income attributable to common shareholders for earnings per share $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares outstanding—basic Additional shares from assumed exercise of stock options ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares outstanding—diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share—basic: Earnings (Loss) from continuing operations $ $ $ ) Earnings from discontinued operations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share—basic $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share—diluted: Earnings (Loss) from continuing operations $ $ $ ) Earnings from discontinued operations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share—diluted $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	May 31, 2017
Employee Benefit Plans
Schedule of change to the entity's projected benefit obligation and the fair value of plan assets for pension plan in the United States and other countries	May 31, 2017 2016 Change in projected benefit obligation: Projected benefit obligation at beginning of year $ $ Service cost Interest cost Participant contributions Net actuarial gain ) ) Benefit payments ) ) Foreign currency translation adjustment ​ ​ ​ ​ ​ ​ ​ ​ Projected benefit obligation at end of year $ $ ​ ​ ​ ​ ​ ​ ​ ​ Change in the fair value of plan assets: Fair value of plan assets at beginning of year $ $ Actual return on plan assets ) Employer contributions Participant contributions Benefit payments ) ) Foreign currency translation adjustment ​ ​ ​ ​ ​ ​ ​ ​ Fair value of plan assets at end of year $ $ ​ ​ ​ ​ ​ ​ ​ ​ Funded status at end of year $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of amounts recognized in the Consolidated Balance Sheets	May 31, 2017 2016 Accrued liabilities $ ) $ ) Other liabilities and deferred income ) ) ​ ​ ​ ​ ​ ​ ​ ​ Funded status at end of year $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of amounts recognized in accumulated other comprehensive loss	May 31, 2017 2016 Actuarial loss $ $ Prior service credit ) ) ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of components of pension expense charged to the consolidated statement of income	For the Year Ended 2017 2016 2015 Service cost $ $ $ Interest cost Expected return on plan assets ) ) ) Curtailment — — Amortization of prior service cost — Recognized net actuarial loss ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of estimated amounts for plans that will be amortized from accumulated other comprehensive loss into expense over the next fiscal year	Net actuarial loss $ Prior service cost — ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of key weighted-average assumptions used in the measurement of the entity's projected benefit obligations	May 31, 2017 2016 Discount rate: Domestic plans % % International plan Rate of compensation increase: Domestic plans % % International plan
Summary of the weighted average assumptions used to determine net periodic pension expense	For the Year 2017 2016 2015 Discount rate: Domestic plans % % % International plan Rate of compensation increase: Domestic plans % % % International plan Expected long-term rate on plan assets: Domestic plans % % % International plan
Schedule of actual asset allocation and target allocations	May 31, Target Asset 2017 2016 Equity securities % % 45 - 75 % Fixed income securities 15 - 25 % Other 0 - 25 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ % % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of fair value of pension plan assets	The following table sets forth by level, within the fair value hierarchy, pension plan assets at their fair value as of May 31, 2017: Level 1 1 Level 2 2 Level 3 3 Total Equity securities: U.S. mutual funds $ $ — $ — $ International mutual funds — — Fixed income: Government securities and corporate bond mutual funds — — Funds-of-funds — Hedge funds — — Cash and cash equivalents — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investments $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following table sets forth by level, within the fair value hierarchy, pension plan assets at their fair value as of May 31, 2016: Level 1 1 Level 2 2 Level 3 3 Total Equity securities: U.S. common stock $ $ — $ — $ U.S. mutual funds — — International common stock — — International mutual funds — — Fixed income: Government securities and corporate bond mutual funds — — Funds-of-funds — Hedge funds — — Cash and cash equivalents — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investments $ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 1 Quoted prices in active markets for identical assets that we have the ability to access as of the reporting date. 2 Inputs other than quoted prices included within Level 1 that are directly observable for the asset or indirectly observable through corroboration with observable market data. 3 Unobservable inputs, such as internally developed pricing models or third party valuations for the asset due to little or no market activity for the asset.
Schedule of reconciliation of Level 3 pension assets measured at fair value	Hedge Funds Fund-of-funds Total Balance as of May 31, 2015 $ $ $ Return on plan assets related to assets still held at May 31, 2016 ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2016 Sales — ) ) Return on plan assets related to assets still held at May 31, 2017 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2017 $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of estimated future pension payments	Fiscal Year 2018 2019 2020 2021 2022 2023 to Estimated future pension payments $ $ $ $ $ $

Accumulated Other Comprehensi34

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	May 31, 2017
Accumulated Other Comprehensive Loss
Schedule of changes in accumulated other comprehensive loss ("AOCL") by component	Currency Pension Derivative Total Balance as of June 1, 2014 $ $ ) $ ) $ ) Other comprehensive income (loss) before reclassifications ) ) ) Sale of Telair Cargo Group — Amounts reclassified from AOCL — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive income (loss) ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2015 ) — ) Reclassifications within AOCL ) — — Other comprehensive income (loss) before reclassifications — ) — ) Amounts reclassified from AOCL — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive loss — ) — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2016 ) ) — ) Other comprehensive loss before reclassifications ) — Amounts reclassified from AOCL — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other comprehensive income (loss) ) — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of May 31, 2017 $ ) $ ) $ — $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	May 31, 2017
Commitments and Contingencies
Schedule of future minimum payments under operating leases	2018 $ 2019 2020 2021 2022 2023 and thereafter

Other Noncurrent Assets (Tables

Other Noncurrent Assets (Tables)	12 Months Ended
	May 31, 2017
Other Noncurrent Assets
Schedule of other noncurrent assets	May 31, 2017 2016 Assets under deferred compensation plan $ $ Costs in excess of billings Cash surrender value of life insurance Investments in joint ventures License fees Other ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	May 31, 2017
ACLAS
Acquisitions
Schedule of fair value of net assets acquired	Inventory $ Equipment on or available for long-term lease Intangible assets ​ ​ ​ ​ ​ Assets acquired $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Vantem Modular LLC
Acquisitions
Schedule of fair value of net assets acquired	Current assets $ Equipment Intangible assets Contingent consideration ) ​ ​ ​ ​ ​ Net assets acquired Goodwill ​ ​ ​ ​ ​ Purchase price $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Business Segment Information (T

Business Segment Information (Tables)	12 Months Ended
	May 31, 2017
Business Segment Information
Schedule of selected financial information for each reportable segment	For the Year Ended May 31, 2017 2016 2015 Net sales: Aviation Services $ $ $ Expeditionary Services ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended May 31, 2017 2016 2015 Gross profit (loss): Aviation Services $ $ $ Expeditionary Services ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ May 31, 2017 2016 2015 Total assets: Aviation Services $ $ $ Expeditionary Services Corporate and discontinued operations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended May 31, 2017 2016 2015 Capital expenditures: Aviation Services $ $ $ Expeditionary Services Corporate ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total continuing operations Discontinued operations — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended May 31, 2017 2016 2015 Depreciation and amortization: 1 Aviation Services $ $ $ Expeditionary Services Corporate ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total continuing operations Discontinued operations — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 1 Includes depreciation and amortization of stock-based compensation.
Schedule of reconciliation of segment gross profit to income (loss) from continuing operations before provision for income taxes	For the Year Ended May 31, 2017 2016 2015 Segment gross profit $ $ $ Selling, general and administrative ) ) ) Earnings (Loss) from joint ventures ) ) Loss on extinguishment of debt — ) ) Interest expense ) ) ) Interest income ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income (Loss) from continuing operations before provision for income taxes $ $ $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of sales to the U.S. Department of Defense, other U.S. government agencies and their contractors by segment	For the Year Ended May 31, 2017 2016 2015 Aviation Services $ $ $ Expeditionary Services ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Percentage of total sales % % % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of sales by type of product/service	For the Year Ended May 31, 2017 2016 2015 Aviation supply chain $ $ $ Maintenance, repair and overhaul services Expeditionary airlift services Mobility products ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of geographic data	May 31, 2017 2016 Long-lived assets: United States $ $ Europe Other ​ ​ ​ ​ ​ ​ ​ ​ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Selected Quarterly Data (Unau39

Selected Quarterly Data (Unaudited) (Tables)	12 Months Ended
	May 31, 2017
Selected Quarterly Data (Unaudited)
Schedule of unaudited selected quarterly data	Fiscal 2017 First Second Third Fourth Full Sales $ $ $ $ $ Gross profit Income from continuing operations Income (Loss) from discontinued operations ) — Net income Earnings (Loss) per share—basic: (1) Continuing operations Discontinued operations ) — Earnings per share—basic Earnings (Loss) per share—diluted: (1) Continuing operations Discontinued operations ) — Earnings per share—diluted Fiscal 2016 First Second Third Fourth Full Sales $ $ $ $ $ Gross profit Income from continuing operations Income (Loss) from discontinued operations (2) ) ) Net income Earnings (Loss) per share—basic: (1) Continuing operations Discontinued operations ) ) — Earnings per share—basic Earnings (Loss) per share—diluted: (1) Continuing operations Discontinued operations ) ) — Earnings per share—diluted 1 The earnings-per-share computation for the year is a separate, annual calculation. Accordingly, the sum of the quarterly earnings-per-share amounts does not necessarily equal the earnings per share for the year. 2 First quarter income from discontinued operations in fiscal 2016 reflects a pre-tax gain of $27.7 million for the receipt of contingent consideration from the sale of Telair Cargo Group in fiscal 2015.

Allowance for Doubtful Accoun40

Allowance for Doubtful Accounts (Tables)	12 Months Ended
	May 31, 2017
Allowance for Doubtful Accounts
Schedule of allowance for doubtful accounts	May 31, 2017 2016 2015 Balance, beginning of year $ $ $ Provision charged to operations Deductions for accounts written off, net of recoveries ) ) ) Sale of Telair Cargo Group — — ) Reclassification to assets of discontinued operations — — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance, end of year $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Summary of Significant Accoun41

Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Revenue Recognition
Recognized net favorable cumulative catch-up adjustments	$ 8.5	$ 3.7	$ 2.5
KC10 Supply Program
Revenue Recognition
Unbilled accounts receivable related to KC10 program	14.5	29.8
KC10 logistics support services
Revenue Recognition
Sales for KC10 logistics support services	110.6	148.1	111.4
Gross profit recognized for KC10 logistics support services	$ 3.7	$ 12	$ 4.5
Minimum
Principles of Consolidation
Percentage of owned aircraft	20.00%
Maximum
Principles of Consolidation
Percentage of owned aircraft	50.00%

Summary of Significant Accoun42

Summary of Significant Accounting Policies - Goodwill (Details) $ in Millions	12 Months Ended
	May 31, 2017USD ($)item	May 31, 2016USD ($)
Goodwill by reportable segment
Total number of reporting units | item	5
Number of reporting units assigned for goodwill | item	4
Goodwill, Beginning Balance	$ 117.3	$ 123.5
Acquisition		1.3
Deferred tax adjustments		(6.5)
Foreign currency translation adjustments	(1.9)	(1)
Goodwill, Ending Balance	$ 115.4	117.3
Aviation Services
Goodwill by reportable segment
Number of reporting units assigned for goodwill | item	2
Goodwill, Beginning Balance	$ 66.3	73.8
Deferred tax adjustments		(6.5)
Foreign currency translation adjustments	(1.9)	(1)
Goodwill, Ending Balance	$ 64.4	66.3
Expeditionary Services
Goodwill by reportable segment
Number of reporting units assigned for goodwill | item	2
Goodwill, Beginning Balance	$ 51	49.7
Acquisition		1.3
Goodwill, Ending Balance	$ 51	$ 51

Summary of Significant Accoun43

Summary of Significant Accounting Policies - Intangibles (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Amortizable intangible assets:
Gross carrying amount	$ 61.5	$ 61
Accumulated Amortization	(29.8)	(26.5)
Net carrying amount	31.7	34.5
Unamortized intangible assets:
Trademarks	1.1	1.3
Intangible Assets, Gross (Excluding Goodwill)	62.6	62.3
Intangible Assets, Net (Excluding Goodwill), Total	32.8	35.8
Amortization expense	4.3	4.4	$ 4.6
Estimated aggregate amortization expense for intangible assets in each of the next five fiscal years
2,018	4.5
2,019	3.8
2,020	3.5
2,021	3.5
2,022	2.7
Customer relationships
Amortizable intangible assets:
Gross carrying amount	24.4	22.7
Accumulated Amortization	(11.6)	(10.5)
Net carrying amount	12.8	12.2
Developed technology
Amortizable intangible assets:
Gross carrying amount	8.8	11.4
Accumulated Amortization	(4.7)	(4.6)
Net carrying amount	4.1	6.8
Lease agreements
Amortizable intangible assets:
Gross carrying amount	22.5	21.5
Accumulated Amortization	(11.2)	(9.9)
Net carrying amount	11.3	11.6
FAA certificates
Amortizable intangible assets:
Gross carrying amount	5.6	5.2
Accumulated Amortization	(2.3)	(1.5)
Net carrying amount	$ 3.3	3.7
Unamortized intangible assets:
Useful life	20 years
Trademarks
Amortizable intangible assets:
Gross carrying amount	$ 0.2	0.2
Net carrying amount	$ 0.2	$ 0.2
Minimum | Customer relationships
Unamortized intangible assets:
Useful life	10 years
Minimum | Developed technology
Unamortized intangible assets:
Useful life	7 years
Minimum | Lease agreements
Unamortized intangible assets:
Useful life	5 years
Maximum | Customer relationships
Unamortized intangible assets:
Useful life	20 years
Maximum | Developed technology
Unamortized intangible assets:
Useful life	15 years
Maximum | Lease agreements
Unamortized intangible assets:
Useful life	18 years

Summary of Significant Accoun44

Summary of Significant Accounting Policies - Financial Instruments (Details) - Accounts receivable - Customer - USD ($) $ in Millions	May 31, 2017	May 31, 2016
U.S. Department of Defense
Financial Instruments and Concentrations of Market or Credit Risk
Accounts receivable due	$ 43	$ 43.7
Large defense contractor
Financial Instruments and Concentrations of Market or Credit Risk
Accounts receivable due	$ 25.5	$ 42.4

Summary of Significant Accoun45

Summary of Significant Accounting Policies - Inventory (Details) $ in Millions	3 Months Ended	12 Months Ended
	May 31, 2015USD ($)aircraft	May 31, 2015USD ($)aircraft	May 31, 2017USD ($)	May 31, 2016USD ($)
Inventories
Raw materials and parts			$ 45	$ 46.3
Work-in-process			25.8	23.4
Aircraft and engine parts, components and finished goods			393.1	366.6
Aircraft held for sale and related support parts			19.2	15.7
Total inventories			$ 483.1	$ 452
Inventory impairment charge		$ 8.9
Sales Proceeds from sale-leaseback advance		$ 40.3
Rotary-wing aircraft
Inventories
Number of aircrafts under sale leaseback transaction | aircraft	2	2
Sale leaseback transaction loss	$ 1.1

Summary of Significant Accoun46

Summary of Significant Accounting Policies - Equipment under Leases (Details) $ in Millions	3 Months Ended	12 Months Ended
	May 31, 2015USD ($)aircraft	May 31, 2017USD ($)	May 31, 2015USD ($)
Equipment under leases
Number of remaining aircraft sold | aircraft	2
Future rent due to us under non-cancelable leases
2,018		$ 31.6
2,019		31.3
2,020		31.2
2,021		30.6
2,022		$ 30.6
Rotable assets
Equipment under leases
Impairment charges of equipment on short-term lease			$ 17.7
Aircraft
Equipment under leases
Proceeds from sale of long term leases	$ 11
Loss on sale of long term leases	$ 14.8
Minimum
Equipment under leases
Period of short-term leases		1 month
Period of long-term lease		12 months
Maximum
Equipment under leases
Period of short-term leases		12 months

Summary of Significant Accoun47

Summary of Significant Accounting Policies - Property, Plant and Equipment and Supplemental Information on Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Supplemental Information on Cash Flows
Interest paid	$ 4.4	$ 4.7	$ 42.7
Income taxes paid	12.7	35.7	105.6
Income tax refunds and interest received	$ 1.3	$ 1.3	$ 12.1
Building and improvements | Minimum
Property, Plant and Equipment
Useful life	10 years
Building and improvements | Maximum
Property, Plant and Equipment
Useful life	40 years
Equipment | Minimum
Property, Plant and Equipment
Useful life	3 years
Equipment | Maximum
Property, Plant and Equipment
Useful life	10 years
Furniture and fixtures | Minimum
Property, Plant and Equipment
Useful life	3 years
Furniture and fixtures | Maximum
Property, Plant and Equipment
Useful life	10 years
Capitalized software | Minimum
Property, Plant and Equipment
Useful life	3 years
Capitalized software | Maximum
Property, Plant and Equipment
Useful life	10 years
Aircraft and components | Minimum
Property, Plant and Equipment
Useful life	7 years
Aircraft and components | Maximum
Property, Plant and Equipment
Useful life	30 years

Summary of Significant Accoun48

Summary of Significant Accounting Policies - Treasury Stock (Details) - USD ($) $ / shares in Units, $ in Millions	May 29, 2015	May 31, 2017	May 31, 2016	May 31, 2015
Repurchase of treasury shares		$ 19.8	$ 18.8	$ 151.5
Shares repurchased (in shares)	4,185,960
Change in treasury stock due to restricted stock grants		5.4	(0.3)	4.2
Change in treasury stock due to exercise of stock options, net of shares withheld to satisfy statutory tax obligations		12	6.7	6.3
Share repurchase price (in dollars per share)	$ 31.90
Cash tender offer amount	$ 133.5
Fees and expenses	$ 1.2
Shares repurchased		16.8
Change in treasury stock due to restricted stock awards and exercise of stock options, net of shares withheld to satisfy statutory tax obligations				3.6
Treasury Stock
Total increase (decrease) in treasury stock		12.2	21.3
Repurchase of treasury shares		19.8	18.8	151.5
Change in treasury stock due to restricted stock grants		(1.3)	(4.8)	(0.7)
Change in treasury stock due to exercise of stock options, net of shares withheld to satisfy statutory tax obligations		$ 8.9	$ 2.3	$ 4.2

Discontinued Operations (Detail

Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2017	Feb. 28, 2017	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	May 31, 2017	May 31, 2016	May 31, 2015
Discontinued Operations
Impairment charges											$ 53
Interest expense									$ 5.5	$ 6.4	27.2
Income from discontinued operations
Provision for income taxes (benefit)	$ (6.7)				$ 2.8
Income from discontinued operations									6.3	9.4	84.3
Income from discontinued operations attributable to AAR	6.1	$ 0.6	$ (0.4)	$ 0.2	$ (5.1)	$ (1.2)	$ 15.5		6.3	9.4	84.1
Cost of Product
Discontinued Operations
Impairment charges											25.6
Telair Cargo Group and PSM | Discontinued Operations, Held-for-sale or Disposed of by Sale
Discontinued Operations
General corporate overhead									0	0	0
Interest expense									0	0	8.5
Assets and liabilities held for sale related to discontinued operations
Liabilities of discontinued operations	$ 6.9			$ 12.5					6.9	12.5
Income from discontinued operations
Sales									0.6	11.5	259.2
Cost of sales									1	15.3	219.7
Selling, general and administrative expenses									1.2	3	26.9
Interest expense, net											9.4
Operating income (loss) from discontinued operations									(1.6)	(6.8)	3.2
Provision for income taxes (benefit)									(7.9)	11.5	85.6
Income from discontinued operations									6.3	9.4	84.3
Income attributable to noncontrolling interest											(0.2)
Income from discontinued operations attributable to AAR									$ 6.3	9.4	84.1
Telair Cargo Group
Discontinued Operations
Gain on sale of assets							27.7
Income from discontinued operations
Gain recognized on sale of business											49.7
Telair Cargo Group | Disposed of by sale
Discontinued Operations
Cash consideration received before fees and expenses								$ 705
Gain on sale of assets								198.6
Telair Cargo Group | A400M | Discontinued Operations, Held-for-sale or Disposed of by Sale
Income from discontinued operations
Gain recognized on sale of business										$ 27.7	198.6
Telair Cargo Group | A400M | Disposed of by sale
Income from discontinued operations
Gain recognized on sale of business							$ 27.7
Telair Cargo Group | A400M | Maximum | Disposed of by sale
Discontinued Operations
Contingent consideration								$ 35
Precision Systems Manufacturing | Discontinued Operations, Held-for-sale or Disposed of by Sale
Income from discontinued operations
PSM Impairment charge											(31.9)
Precision Systems Manufacturing | Discontinued Operations, Held-for-sale
Income from discontinued operations
PSM Impairment charge											$ 57.5

Financing Arrangements (Details

Financing Arrangements (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2015	May 31, 2017	May 31, 2016	May 31, 2015	Mar. 24, 2015
Financing Arrangements
Total debt		$ 159.3	$ 150.1
Current maturities of debt		(2)	(12)
Debt issuance costs, net		(2)	(2)
Long-term debt		155.3	136.1
Short-term borrowing activity
Loss on extinguishment of debt			0.4	$ 44.9
Credit Facility Amendment
Financing Arrangements
Maximum borrowing capacity					$ 500
Capital lease obligations
Financing Arrangements
Total debt		3.3	5.1
New capital leases related to new aircraft and IT equipment			5.1
Revolving Credit Facility expiring November 1, 2021 with interest payable monthly
Financing Arrangements
Total debt		$ 131	110
Revolving Credit Facility expiring November 1, 2021 with interest payable monthly | Eurodollar rate | Minimum
Financing Arrangements
Basis spread on variable rate under the credit agreement after amendment (as a percent)		1.00%
Revolving Credit Facility expiring November 1, 2021 with interest payable monthly | Eurodollar rate | Maximum
Financing Arrangements
Basis spread on variable rate under the credit agreement after amendment (as a percent)		2.00%
Revolving Credit Facility expiring November 1, 2021 with interest payable monthly | Base rate | Minimum
Financing Arrangements
Basis spread on variable rate under the credit agreement after amendment (as a percent)		0.00%
Revolving Credit Facility expiring November 1, 2021 with interest payable monthly | Base rate | Maximum
Financing Arrangements
Basis spread on variable rate under the credit agreement after amendment (as a percent)		1.00%
Industrial revenue bond (secured by property, plant and equipment) due August 1, 2018 with interest payable monthly
Financing Arrangements
Total debt		$ 25	25
Note payable due March 9, 2017 with floating interest rate, payable semi-annually on June 1 and December 1
Financing Arrangements
Total debt			10
Secured credit facility (secured by aircraft and related engines and components) due April 23, 2015 with floating interest rate, payable monthly
Short-term borrowing activity
Amount outstanding		9.6
Notes payable due January 15, 2022 with interest at 7.25% payable semi-annually on January 15 and July 15
Financing Arrangements
Interest rate (as a percent)	7.25%
Short-term borrowing activity
Redemption value of senior notes	$ 325
Redemption value including make-whole premium	370.6
Loss on extinguishment of debt	44.9
Make-whole premium of redeemed notes	45.6
Unamortized deferred financing cost	6.2
Unamortized deferred cost offset	$ 6.9
Convertible notes payable
Interest expense
Coupon interest			0.6	1.5
Amortization of deferred financing fees			0.1	0.1
Amortization of discount			1.3	2.4
Interest expense related to convertible notes			2	4
Variable rate and fixed rate debt | Significant other observable inputs (Level 2)
Financing Arrangements
Estimated fair value of long-term debt		156
Credit Agreement and its Predecessor
Short-term borrowing activity
Maximum amount borrowed		217	200	215
Average daily borrowings		$ 175.5	$ 134.2	$ 140.7
Average interest rate during the year (as a percent)		1.77%	1.41%	1.69%
Revolving credit facility | Credit Facility Amendment
Financing Arrangements
Increase in borrowing capacity		$ 250
Total borrowing capacity		$ 750

Derivative Instruments and He51

Derivative Instruments and Hedging Activities (Details) $ in Millions	May 31, 2015USD ($)item
Derivative Instruments and Hedging Activities
Number of derivative financial instruments | item	2
Interest rate cap | Derivatives designated as hedging instruments: | Cash flow hedges
Derivative Instruments and Hedging Activities
Notional amount under revolving credit agreement	$ 50
Interest rate swap | Derivatives designated as hedging instruments: | Cash flow hedges
Derivative Instruments and Hedging Activities
Notional amount under revolving credit agreement	50
Interest Rate Swap and Cap Agreements | Derivatives designated as hedging instruments:
Derivative Instruments and Hedging Activities
Settlement of floating-to-fixed interest rate swap and interest rate cap agreement	$ 2.6

Derivative Instruments and He52

Derivative Instruments and Hedging Activities - Impact on Statement of Income (Details) $ in Millions	12 Months Ended
	May 31, 2015USD ($)
Derivative Instruments and Hedging Activities
Loss recognized related to the reclassification of previously unrealized losses in accumulated other comprehensive loss	$ 2

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) $ / shares in Units, $ in Millions	12 Months Ended
	May 31, 2017USD ($)item$ / sharesshares	May 31, 2016USD ($)$ / sharesshares	May 31, 2015USD ($)$ / sharesshares
Share-Based Compensation
Total number of shares granted since inception	11,149,000
2013 Stock Plan
Share-Based Compensation
Shares available for future grant	2,689,733
Stock options
Share-Based Compensation
Expiration term	10 years
First number of equal annual increments in which stock options are exercisable | item	3
First number of equal annual increments in which stock options are exercisable | item	4
First number of equal annual increments in which stock options are exercisable | item	5
Commencement period after the date of grant for annual increments of stock options becoming exercisable	1 year
Granted (in shares)			0
Weighted average fair value of stock options granted (in dollars per share) | $ / shares	$ 6.50	$ 7.48
Assumptions used in the Black-Scholes option pricing models to estimate the fair value of each stock option grant
Risk-free interest rate	1.00%	1.60%
Expected volatility of common stock	36.80%	36.10%
Dividend yield	1.30%	1.10%
Expected option term in years	4 years	4 years 2 months 12 days
Shares
Outstanding at beginning of year (in shares)	2,096,000	1,857,000	2,753,000
Granted (in shares)	687,000	488,767
Exercised (in shares)	(396,000)	(122,000)	(793,000)
Cancelled (in shares)	(53,000)	(128,000)	(103,000)
Outstanding at end of year (in shares)	2,334,000	2,096,000	1,857,000
Options exercisable at end of year (in shares)	910,000	837,000	627,000
Weighted Average Exercise Price
Outstanding at beginning of year (in dollars per share) | $ / shares	$ 22.17	$ 21.05	$ 19.59
Granted (in dollars per share) | $ / shares	24.10	26.62
Exercised (in dollars per share) | $ / shares	20.07	20.61	15.98
Cancelled (in dollars per share) | $ / shares	25.42	24.47	21.03
Outstanding at end of year (in dollars per share) | $ / shares	23.02	22.17	21.05
Options exercisable at end of year (in dollars per share) | $ / shares	$ 21.97	$ 21.21	$ 21.78
Stock options, additional disclosures
Total fair value of stock options vested | $	$ 3.5	$ 2.7	$ 3.1
Total intrinsic value of stock options exercised | $	4.7	1	11.1
Aggregate intrinsic value of options outstanding | $	27.8	7.4
Tax benefit realized from stock options exercised | $	1.2	0.2	2.4
Unearned compensation not yet recognized | $	$ 5.5
Average remaining amortization period of unearned compensation	9 months 18 days
Stock options | Selling, general and administrative expenses
Stock options, additional disclosures
Compensation expense | $	$ 4.6	3.5	2.7
Restricted stock
Share-Based Compensation
Granted (in shares)	302,000
Stock options, additional disclosures
Unearned compensation not yet recognized | $	$ 5.5
Average remaining amortization period of unearned compensation	2 years 1 month 6 days
Restricted stock | Selling, general and administrative expenses
Stock options, additional disclosures
Compensation expense | $	$ 6.4	$ 3.2	$ 4.7
Restricted stock | 2013 Stock Plan
Share-Based Compensation
Granted (in shares)	2,018,000
Restricted stock | Minimum
Share-Based Compensation
Vesting period	1 year
Restricted stock | Maximum
Share-Based Compensation
Vesting period	5 years
Performance-based restricted stock | Minimum
Share-Based Compensation
Vesting period	3 years
Performance-based restricted stock | Maximum
Share-Based Compensation
Vesting period	5 years
Time-based restricted stock | Board of Directors
Share-Based Compensation
Granted (in shares)	50,625	47,083	45,000

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Options (Details) shares in Thousands	12 Months Ended
	May 31, 2017$ / sharesshares
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	2,334
Weighted-Average Remaining Contractual Life in Years	6 years 9 months 18 days
Weighted-Average Exercise Price (in dollars per Share)	$ 23.02
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	910
Weighted-Average Exercise Price (in dollar per Share)	$ 21.97
$12.00 - $20.00
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	12
Option Exercise Price Range, high end of range (in dollars per share)	$ 20
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	500
Weighted-Average Remaining Contractual Life in Years	4 years 4 months 24 days
Weighted-Average Exercise Price (in dollars per Share)	$ 14.02
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	349
Weighted-Average Exercise Price (in dollar per Share)	$ 14.49
$20.01 - $26.00
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	20.01
Option Exercise Price Range, high end of range (in dollars per share)	$ 26
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	1,305
Weighted-Average Remaining Contractual Life in Years	7 years 7 months 6 days
Weighted-Average Exercise Price (in dollars per Share)	$ 24.72
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	322
Weighted-Average Exercise Price (in dollar per Share)	$ 25.44
$26.01 - $34.50
Share-Based Compensation
Option Exercise Price Range, low end of range (in dollars per share)	26.01
Option Exercise Price Range, high end of range (in dollars per share)	$ 34.50
Options Outstanding
Number Outstanding at the end of the period (in shares) | shares	529
Weighted-Average Remaining Contractual Life in Years	7 years 2 months 12 days
Weighted-Average Exercise Price (in dollars per Share)	$ 27.36
Options Exercisable
Number Outstanding at the end of the period (in shares) | shares	239
Weighted-Average Exercise Price (in dollar per Share)	$ 28.25

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Restricted stock
Number of Shares
Nonvested at the beginning of the period ( in shares)	400,000
Granted (in shares)	302,000
Vested (in shares)	(98,000)
Forfeited (in shares)	(9,000)
Nonvested at the end of the period (in shares)	595,000	400,000
Weighted Average Fair Value on Grant Date
Nonvested at the beginning of the period (in dollars per share)	$ 25.61
Granted (in dollars per share)	24.24
Vested (in dollars per share)	21.98
Forfeited (in dollars per share)	26.32
Nonvested at the end of the period (in dollars per share)	$ 25.93	$ 25.61
Unearned compensation not yet recognized	$ 5.5
Average remaining amortization period of unearned compensation	2 years 1 month 6 days
Restricted stock | Selling, general and administrative expenses
Restricted Stock
Compensation expense	$ 6.4	$ 3.2	$ 4.7
Performance-based restricted stock | Executives and other key employees
Number of Shares
Granted (in shares)	212,583	119,929	188,125
Time-based restricted stock | Board of Directors
Number of Shares
Granted (in shares)	50,625	47,083	45,000
Time-based restricted stock | Executives and other key employees
Number of Shares
Granted (in shares)	39,100	42,557	97,581

Stock-Based Compensation - Shar

Stock-Based Compensation - Shareholders' Rights Plan (Details) - Shareholders' Rights Plan	12 Months Ended
	May 31, 2017item$ / sharesshares
Shareholders' Rights Plan
Right to purchase number of shares | shares	1
Purchase price per share (in dollars per share)	$ 140
Minimum percentage of the common stock shares acquired by a person or group of persons before rights become exercisable	15.00%
Market values of shares under the right (in dollars per share)	$ 280
Market values of shares under the right, as multiplier of exercise price | item	2
Minimum percentage of assets or earning power sold before rights become exercisable	50.00%
Redemption price per Right (in dollars per share)	$ 0.01

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	May 31, 2017	Feb. 29, 2016	May 31, 2017	May 31, 2016	May 31, 2015
Current:
Federal			$ 20.2	$ 10.6	$ 11.4
State			0.2	0.4	0.4
Foreign			3.1	3.8	1.5
Total current			23.5	14.8	13.3
Deferred			0.6	4.8	(52.6)
Provision for income tax (benefit)			$ 24.1	$ 19.6	$ (39.3)
U.S. federal statutory income tax rate (as a percent)			35.00%	35.00%	35.00%
Reasons for difference between the provision for income taxes on pre-tax income from the amount computed by applying the U.S. federal statutory tax rate
Provision for income tax (benefit) at the federal statutory rate			$ 26	$ 20.3	$ (39.6)
State income taxes, net of federal benefit and refunds			0.2	0.2	0.2
Federal adjustments			0.1	0.4	0.1
State net operating losses			(5.7)	(1.1)	(0.1)
Valuation allowance for state deferred tax assets			5.7	1.1	0.1
Prior period adjustments				(1.3)
Effective settlement of prior tax position			2.2
Provision for income tax (benefit)			24.1	19.6	(39.3)
Income tax expense in discontinued operations	$ (6.7)	$ 2.8
Income tax expense in continued operations			24.1	19.6	(39.3)
Income (Loss) before provision for income tax (benefit)			74.3	57.9	(113.2)
Deferred tax assets:
Inventory costs	21.3		21.3	19.9
Impairments	5.6		5.6	9.4
Advanced billings	1.7		1.7	11.1
Postretirement benefits	6.8		6.8	12
Employee benefits	12.3		12.3	10
State NOLs, tax credits and incentives	9.4		9.4	6.5
Other	1.7		1.7	0.6
Total deferred tax assets	58.8		58.8	69.5
Valuation allowance	(10.4)		(10.4)	(4.7)
Total deferred tax assets net of valuation allowance	48.4		48.4	64.8
Deferred tax liabilities:
Tangible and intangible assets	(85.5)		(85.5)	(99)
Other	(0.1)		(0.1)	(0.1)
Total deferred tax liabilities	(85.6)		(85.6)	(99.1)
Net deferred tax liabilities	(37.2)		(37.2)	(34.3)
Reconciliation of unrecognized tax benefits
Beginning balance			12.9	2.2	2.2
Additions for tax positions of prior years			0.4	10.7
Effective settlement of prior tax position			(8.9)
End balance	4.4		$ 4.4	12.9	2.2
Unrecognized tax benefit resulting from statute lapse	2.2
Minimum
Deferred tax liabilities:
Period for net operating losses carry forward (in years)			5 years
Maximum
Deferred tax liabilities:
Period for net operating losses carry forward (in years)			20 years
Accrued Liabilities
Deferred tax liabilities:
Income tax payable	$ 12.3		$ 12.3	1.1
Domestic
Reasons for difference between the provision for income taxes on pre-tax income from the amount computed by applying the U.S. federal statutory tax rate
Income (Loss) before provision for income tax (benefit)			54.9	44.7	(124.4)
Foreign
Reasons for difference between the provision for income taxes on pre-tax income from the amount computed by applying the U.S. federal statutory tax rate
Income (Loss) before provision for income tax (benefit)			$ 19.4	$ 13.2	$ 11.2
Immaterial errors
Reasons for difference between the provision for income taxes on pre-tax income from the amount computed by applying the U.S. federal statutory tax rate
Accrued Income Taxes		0.2
Corrections
Reasons for difference between the provision for income taxes on pre-tax income from the amount computed by applying the U.S. federal statutory tax rate
Income tax expense in discontinued operations		1.5
Income tax expense in continued operations		$ 1.3

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2017	May 31, 2016	May 31, 2015
Earnings Per Share
Effect to the participating securities as result of net loss									$ 0
Basic and Diluted EPS:
Income (Loss) from continuing operations	$ 15.1	$ 13.1	$ 12.1	$ 9.9	$ 11.8	$ 9.9	$ 9.2	$ 7.4	50.2	$ 38.3	$ (73.9)
Less income attributable to participating shares									(0.5)	(0.4)	(0.3)
Income (Loss) from continuing operations attributable to common shareholders									49.7	37.9	(74.2)
Income from discontinued operations attributable to common shareholders	$ 6.1	$ 0.6		$ (0.4)	$ 0.2	$ (5.1)	$ (1.2)	$ 15.5	6.3	9.4	84.1
Net income attributable to common shareholders for earnings per share									$ 56	$ 47.3	$ 9.9
Weighted Average Shares:
Weighted average common shares outstanding - basic									33,900,000	34,400,000	39,100,000
Additional shares from assumed exercise of stock options									400,000	200,000	300,000
Weighted average common shares outstanding - diluted									34,300,000	34,600,000	39,400,000
Earnings per share - basic:
Earnings (Loss) from continuing operations	$ 0.44	$ 0.39	$ 0.35	$ 0.29	$ 0.35	$ 0.29	$ 0.26	$ 0.21	$ 1.47	$ 1.10	$ (1.90)
Earnings from discontinued operations	0.18	0.02		(0.01)		(0.15)	(0.03)	0.44	0.19	0.27	2.16
Earnings per share - basic	0.62	0.41	0.35	0.28	0.35	0.14	0.23	0.65	1.66	1.37	0.26
Earnings per share - diluted:
Earnings (Loss) from continuing operations	0.44	0.38	0.35	0.29	0.34	0.29	0.26	0.21	1.45	1.10	(1.90)
Earnings from discontinued operations	0.18	0.02		(0.01)		(0.15)	(0.03)	0.44	0.19	0.27	2.14
Earnings per share - diluted	$ 0.62	$ 0.40	$ 0.35	$ 0.28	$ 0.34	$ 0.14	$ 0.23	$ 0.65	$ 1.64	$ 1.37	$ 0.24
Antidilutive stock options excluded from the computation of diluted earnings per share (in shares)									11,200	1,374,200	168,200

Employee Benefit Plans (Details

Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Cash balance pension plan
Employee benefit plans
Interest crediting rate as a percentage of average 30-year treasury rate	100.00%
Average period of treasury rate used in determination of interest crediting rate	30 years
Average interest crediting rate (as a percent)	4.50%
Defined Benefit Pension Plans
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 145.7	$ 144.9
Service cost	2.5	2.5
Interest cost	4.2	4.5
Participant contributions	0.3	0.3
Net actuarial gain	(2)	(1.1)
Benefit payments	(6)	(6)
Foreign currency translation adjustment	0.7	0.6
Projected benefit obligation at end of year	145.4	145.7	$ 144.9
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	111	115.8
Actual return on plan assets	9.9	(3)
Employer contributions	2.9	3.4
Participant contributions	0.3	0.3
Benefit payments	(6)	(6)
Foreign currency translation adjustment	0.7	0.5
Fair value of plan assets at end of year	118.8	111	115.8
Funded status at end of year	(26.6)	(34.7)
Amounts recognized in the consolidated balance sheets
Accrued liabilities	(2.7)	(3.8)
Other liabilities and deferred income	(23.9)	(30.9)
Funded status at end of year	(26.6)	(34.7)
Amounts recognized in accumulated other comprehensive loss
Actuarial loss		58.8	66.4
Prior service credit		(0.4)	(0.4)
Total		58.4	66
Accumulated benefit obligation	140
Net Periodic Benefit Cost
Service cost	2.5	2.5	2
Interest cost	4.2	4.5	4.8
Expected return on plan assets	(6.5)	(6.5)	(6)
Curtailment			0.2
Amortization of prior service cost		0.1	0.2
Recognized net actuarial loss	2.4	2.4	1.8
Total	2.6	$ 3	$ 3
Estimated amounts that will be amortized from accumulated other comprehensive loss into expense over the next fiscal year
Net actuarial loss	2.3
Total	$ 2.3
Defined Benefit Pension Plans | Board of Directors
Employee benefit plans
Benefits paid in cash as percentage of the annual retainer fees payable to active outside director	25.00%
Defined Benefit Pension Plans | Minimum | Board of Directors
Employee benefit plans
Minimum age of retirement	65 years
Required minimum years of service as a director	5 years
Defined Benefit Pension Plans | Maximum | Board of Directors
Employee benefit plans
Period for which benefits will be payable	10 years
Domestic plans
Key weighted-average assumptions used in the measurement of the company's projected benefit obligations
Discount rate (as a percent)	3.82%	3.83%
Rate of compensation increase (as a percent)	2.50%	2.50%
Weighted-average assumptions used to determine net periodic pension expense
Discount rate: (as a percent)	3.83%	4.15%	4.23%
Rate of compensation increase: (as a percent)	2.50%	2.50%	2.50%
Expected long-term rate on plan assets: (as a percent)	7.25%	7.25%	7.50%
Plan Assets
Actual asset allocation (as a percent)	100.00%	100.00%
Domestic plans | Equity securities
Plan Assets
Actual asset allocation (as a percent)	62.00%	59.00%
Domestic plans | Fixed income securities
Plan Assets
Actual asset allocation (as a percent)	16.00%	17.00%
Domestic plans | Other
Plan Assets
Actual asset allocation (as a percent)	22.00%	24.00%
Domestic plans | Minimum | Equity securities
Plan Assets
Target Asset Allocation (as a percent)	45.00%
Domestic plans | Minimum | Fixed income securities
Plan Assets
Target Asset Allocation (as a percent)	15.00%
Domestic plans | Minimum | Other
Plan Assets
Target Asset Allocation (as a percent)	0.00%
Domestic plans | Maximum | Equity securities
Plan Assets
Target Asset Allocation (as a percent)	75.00%
Domestic plans | Maximum | Fixed income securities
Plan Assets
Target Asset Allocation (as a percent)	25.00%
Domestic plans | Maximum | Other
Plan Assets
Target Asset Allocation (as a percent)	25.00%
International plans
Key weighted-average assumptions used in the measurement of the company's projected benefit obligations
Discount rate (as a percent)	2.00%	1.90%
Rate of compensation increase (as a percent)	3.00%	3.00%
Weighted-average assumptions used to determine net periodic pension expense
Discount rate: (as a percent)	1.90%	1.90%	1.90%
Rate of compensation increase: (as a percent)	3.00%	3.00%	3.00%
Expected long-term rate on plan assets: (as a percent)	4.00%	4.00%	4.00%

Employee Benefit Plans - Reconc

Employee Benefit Plans - Reconciliation of Pension Assets (Details) - Defined Benefit Pension Plans - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016
Employee benefit plans
Fair value of plan assets	$ 111	$ 115.8
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	111	115.8
Fair value of plan assets at end of year	118.8	111
Total
Employee benefit plans
Fair value of plan assets	111	111
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	111
Fair value of plan assets at end of year	118.8	111
U.S. common stock | Total
Employee benefit plans
Fair value of plan assets	2.3	2.3
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	2.3
Fair value of plan assets at end of year		2.3
U.S. mutual funds | Total
Employee benefit plans
Fair value of plan assets	24.6	24.6
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	24.6
Fair value of plan assets at end of year	30.6	24.6
International common stock | Total
Employee benefit plans
Fair value of plan assets	0.1	0.1
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	0.1
Fair value of plan assets at end of year		0.1
International mutual funds | Total
Employee benefit plans
Fair value of plan assets	7.9	7.9
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	7.9
Fair value of plan assets at end of year	9.5	7.9
Government securities and corporate bond mutual funds | Total
Employee benefit plans
Fair value of plan assets	9.9	9.9
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	9.9
Fair value of plan assets at end of year	10.1	9.9
Funds-of-funds | Total
Employee benefit plans
Fair value of plan assets	57.7	57.7
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	57.7
Fair value of plan assets at end of year	58.9	57.7
Hedge funds | Total
Employee benefit plans
Fair value of plan assets	6.6	6.6
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	6.6
Fair value of plan assets at end of year	6.8	6.6
Cash and cash equivalents | Total
Employee benefit plans
Fair value of plan assets	1.9	1.9
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	1.9
Fair value of plan assets at end of year	2.9	1.9
Quoted prices in active markets (Level 1)
Employee benefit plans
Fair value of plan assets	46.7	46.7
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	46.7
Fair value of plan assets at end of year	53.1	46.7
Quoted prices in active markets (Level 1) | U.S. common stock
Employee benefit plans
Fair value of plan assets	2.3	2.3
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	2.3
Fair value of plan assets at end of year		2.3
Quoted prices in active markets (Level 1) | U.S. mutual funds
Employee benefit plans
Fair value of plan assets	24.6	24.6
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	24.6
Fair value of plan assets at end of year	30.6	24.6
Quoted prices in active markets (Level 1) | International common stock
Employee benefit plans
Fair value of plan assets	0.1	0.1
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	0.1
Fair value of plan assets at end of year		0.1
Quoted prices in active markets (Level 1) | International mutual funds
Employee benefit plans
Fair value of plan assets	7.9	7.9
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	7.9
Fair value of plan assets at end of year	9.5	7.9
Quoted prices in active markets (Level 1) | Government securities and corporate bond mutual funds
Employee benefit plans
Fair value of plan assets	9.9	9.9
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	9.9
Fair value of plan assets at end of year	10.1	9.9
Quoted prices in active markets (Level 1) | Cash and cash equivalents
Employee benefit plans
Fair value of plan assets	1.9	1.9
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	1.9
Fair value of plan assets at end of year	2.9	1.9
Significant other observable inputs (Level 2)
Employee benefit plans
Fair value of plan assets	50.2	50.2
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	50.2
Fair value of plan assets at end of year	51.6	50.2
Significant other observable inputs (Level 2) | Funds-of-funds
Employee benefit plans
Fair value of plan assets	50.2	50.2
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	50.2
Fair value of plan assets at end of year	51.6	50.2
Significant other unobservable inputs (Level 3)
Employee benefit plans
Fair value of plan assets	14.1	15.1
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	14.1	15.1
Sales	(0.8)
Return on plan assets related to assets still held	0.8	(1)
Fair value of plan assets at end of year	14.1	14.1
Significant other unobservable inputs (Level 3) | Funds-of-funds
Employee benefit plans
Fair value of plan assets	7.5	8
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	7.5	8
Sales	(0.8)
Return on plan assets related to assets still held	0.6	(0.5)
Fair value of plan assets at end of year	7.3	7.5
Significant other unobservable inputs (Level 3) | Hedge funds
Employee benefit plans
Fair value of plan assets	6.6	7.1
Change in the fair value of plan assets:
Fair value of plan assets at beginning of year	6.6	7.1
Return on plan assets related to assets still held	0.2	(0.5)
Fair value of plan assets at end of year	$ 6.8	$ 6.6

Employee Benefit Plans - Future

Employee Benefit Plans - Future Benefit Payments and Defined Contribution Plan (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Defined Contribution Plan
Vesting period	3 years
Expense charged to statement of income	$ 12.7	$ 11.2	$ 12.1
Maximum
Defined Contribution Plan
Maximum percentage of pretax compensation that can be contributed by employees' for 401 (k) defined contribution plan	75.00%
Maximum matching contribution of employer for 401 (k) defined contribution plan (as a percent)	5.00%
Defined Benefit Pension Plans
Estimated future pension payments
2,018	$ 8.9
2,019	5.6
2,020	6.2
2,021	5.9
2,022	5.9
2023 to 2027	35
Funded status
Unfunded projected benefit obligation	26.6	34.7
Domestic plans
Estimated future pension payments
Anticipated contribution in next fiscal year	9.5
Postretirement Benefits Other Than Pensions
Funded status
Unfunded projected benefit obligation	$ 0.7	$ 0.9

Accumulated Other Comprehensi62

Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Accumulated Other Comprehensive Loss
Balance at beginning of the period	$ (44.4)	$ (40.4)	$ (29.3)
Other comprehensive income (loss) before reclassifications from AOCL	2.9	(5.6)	(64.2)
Amounts reclassified from AOCL	1.6	1.6	3.4
Total other comprehensive income (loss), net of tax	4.5	(4)	(11.1)
Balance at end of the period	(39.9)	(44.4)	(40.4)
Currency Translation Adjustments
Accumulated Other Comprehensive Loss
Balance at beginning of the period	(1.1)	0.9	8.7
Reclassification within AOCL		(2)
Other comprehensive income (loss) before reclassifications from AOCL	(0.6)		(56.9)
Total other comprehensive income (loss), net of tax	(0.6)		(7.8)
Balance at end of the period	(1.7)	(1.1)	0.9
Pensions Plans
Accumulated Other Comprehensive Loss
Balance at beginning of the period	(43.3)	(41.3)	(35.4)
Reclassification within AOCL		2
Other comprehensive income (loss) before reclassifications from AOCL	3.5	(5.6)	(7.9)
Amounts reclassified from AOCL	1.6	1.6	1.4
Total other comprehensive income (loss), net of tax	5.1	(4)	(5.9)
Balance at end of the period	$ (38.2)	$ (43.3)	(41.3)
Derivative Instruments
Accumulated Other Comprehensive Loss
Balance at beginning of the period			(2.6)
Other comprehensive income (loss) before reclassifications from AOCL			0.6
Amounts reclassified from AOCL			2
Total other comprehensive income (loss), net of tax			2.6
Telair Cargo Group
Accumulated Other Comprehensive Loss
Gain recognized on sale of business			49.7
Telair Cargo Group | Currency Translation Adjustments
Accumulated Other Comprehensive Loss
Gain recognized on sale of business			49.1
Telair Cargo Group | Pensions Plans
Accumulated Other Comprehensive Loss
Gain recognized on sale of business			$ 0.6

Aircraft Portfolio - Joint Vent

Aircraft Portfolio - Joint Venture (Details) $ in Millions	12 Months Ended
	May 31, 2017USD ($)aircraft	May 31, 2016USD ($)	May 31, 2015USD ($)
Aircraft portfolio
Equity investments	$ 15	$ 17.6
Sales from services	$ 811	764.5	$ 704.7
Owned Through Joint Ventures
Aircraft portfolio
Owned aircraft, number | aircraft	2
Membership interest in joint ventures (as a percent)	50.00%
Sales from services	$ 1.2	0.9	$ 0.1
Owned Through Joint Ventures | Other Noncurrent Assets
Aircraft portfolio
Equity investments	$ 10.7	$ 15

Aircraft Portfolio - Aircraft i

Aircraft Portfolio - Aircraft information (Details) $ in Millions	3 Months Ended
	May 31, 2015USD ($)aircraft	May 31, 2017aircraft
Owned Through Joint Ventures
Aircraft portfolio
Owned aircraft, number | aircraft		2
Percentage of owned aircraft		50.00%
Wholly-Owned
Aircraft portfolio
Percentage of owned aircraft	100.00%
Number of Aircraft Sold | aircraft	2
Proceeds from sale of aircraft	$ 11
Carrying value of aircraft sold	25.8
Loss on sale of aircraft	$ 14.8

Commitments and Contingencies -

Commitments and Contingencies - Aircraft Sale-Leaseback (Details) $ in Millions	Oct. 03, 2003USD ($)	May 31, 2015USD ($)aircraft	May 31, 2016USD ($)aircraft	May 31, 2015USD ($)aircraft	May 31, 2017USD ($)
Aircraft Sale-Leaseback Transactions
Proceeds from sale-leaseback				$ 40.3
Garden City lease
Aircraft Sale-Leaseback Transactions
Proceeds from sale-leaseback	$ 14
Cost of the facility	9.5
Accumulated depreciation of the facility	4.6
Deferred gain realized on the sale	$ 9.1
Deferred gain amortization period	20 years
Unamortized balance of the deferred gain			$ 3.4		$ 2.9
S-92 rotary-wing aircraft
Aircraft Sale-Leaseback Transactions
Proceeds from sale-leaseback				$ 40.3
Number of aircrafts involved in sale leaseback transaction | aircraft		2		2
Sale leaseback transaction loss		$ 1.1
AW-189 rotary-wing aircraft
Aircraft Sale-Leaseback Transactions
Proceeds from sale-leaseback			38.5
Deferred gain realized on the sale			$ 1.7
Deferred gain amortization period			10 years
Number of aircrafts involved in sale leaseback transaction | aircraft			2

Commitments and Contingencies66

Commitments and Contingencies - Operating Lease, Rental Expense, Purchase Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Aggregate amount of purchase obligations due in each of the next five fiscal years
2,018	$ 231.2
2,019	37.7
2,020	1.4
2,021	2.7
2,022	0
Letters of credit and performance bonds outstanding	13.6
Facilities and Equipment
Future minimum payments under operating leases
2,018	24
2,019	18.1
2,020	16.5
2,021	14.4
2,022	13.5
2023 and thereafter	40
Rental expense
Rental expense, net	$ 31.9	$ 33.5	$ 33.7

Other Noncurrent Assets (Detail

Other Noncurrent Assets (Details) - USD ($) $ in Millions	May 31, 2017	May 31, 2016
Other Noncurrent Assets
Assets under deferred compensation plan	$ 32.1	$ 28.8
Costs in excess of billings	19.1	14.9
Cash surrender value of life insurance	17.8	17.7
Investments in joint ventures	15	17.6
License fees	14.4	15.5
Other	7.5	7.5
Other Assets, Noncurrent, Total	$ 105.9	$ 102

Other Noncurrent Assets - Licen

Other Noncurrent Assets - License Fees (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2011	May 31, 2017	May 31, 2016
Intangible assets
License fees		$ 14.4	$ 15.5
Exclusive distribution rights | Unison Industries
Intangible assets
Term of agreement	10 years
Amount agreed to be paid	$ 20
Amount paid	$ 7
Amount payable in each calendar year			1.3
Licensing Agreements | Unison Industries
Intangible assets
License fees		$ 7.2	$ 8.8
Amortization period		10 years
Current portion of the deferred payments		$ 1.3
Long-term portion		$ 3.2

Acquisition (Details)

Acquisition (Details) $ in Millions	Apr. 10, 2017USD ($)aircraft	Dec. 04, 2015USD ($)	May 31, 2017USD ($)	May 31, 2016USD ($)	May 31, 2015USD ($)
Fair value of net assets acquired
Goodwill			$ 115.4	$ 117.3	$ 123.5
ACLAS
Acquisitions
Number of aircrafts under multi-year component support and repair contract | aircraft	100
Deferred consideration payable period	3 years
Fair value of net assets acquired
Inventory	$ 5
Equipment on or available for long-term lease	7
Intangible assets	3
Net assets acquired	$ 15
Vantem Modular LLC
Fair value of net assets acquired
Current assets		$ 1.5
Equipment		0.5
Intangible assets		3.5
Contingent consideration		(2)
Net assets acquired		3.5
Goodwill		1.3
Purchase price		4.8
Vantem Modular LLC | Maximum
Acquisitions
Future royalties		$ 5

Business Segment Information -

Business Segment Information - Segment Data (Details) $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2017USD ($)	Feb. 28, 2017USD ($)	Nov. 30, 2016USD ($)	Aug. 31, 2016USD ($)	May 31, 2016USD ($)	Feb. 29, 2016USD ($)	Nov. 30, 2015USD ($)	Aug. 31, 2015USD ($)	May 31, 2017USD ($)segment	May 31, 2016USD ($)	May 31, 2015USD ($)
Business Segment Information
Number of business segments | segment									2
Net sales	$ 492.3	$ 446.7	$ 423.8	$ 404.8	$ 468.6	$ 412.1	$ 431.5	$ 386.7	$ 1,767.6	$ 1,698.9	$ 1,621.4
Gross profit	79.8	$ 69	$ 66.2	$ 61.5	65.6	$ 59.3	$ 59.1	$ 53.9	276.5	237.9	130.8
Total assets	1,504.1				1,456				1,504.1	1,456	1,454.1
Capital expenditures									33.6	89	46.3
Depreciation and amortization, including depreciation and amortization of stock-based compensation, Net									63.9	57.8	76.9
Continuing operations
Business Segment Information
Capital expenditures									33.6	88.9	42.1
Depreciation and amortization, including depreciation and amortization of stock-based compensation, Gross									63.9	57.8	65.4
Discontinued operations
Business Segment Information
Capital expenditures										0.1	4.2
Depreciation and amortization, including depreciation and amortization of stock-based compensation, Gross											11.5
Aviation Services
Business Segment Information
Net sales									1,485.4	1,425	1,316.1
Gross profit									246.2	229.8	143.8
Total assets	1,057				944.8				1,057	944.8	919
Aviation Services | Continuing operations
Business Segment Information
Capital expenditures									15	16.4	8.7
Depreciation and amortization, including depreciation and amortization of stock-based compensation, Gross									30.8	26.2	28.9
Expeditionary Services
Business Segment Information
Net sales									282.2	273.9	305.3
Gross profit									30.3	8.1	(13)
Total assets	338.8				384.8				338.8	384.8	406
Expeditionary Services | Continuing operations
Business Segment Information
Capital expenditures									10.4	50.4	20.3
Depreciation and amortization, including depreciation and amortization of stock-based compensation, Gross									22.2	24.9	26.9
Corporate | Continuing operations
Business Segment Information
Capital expenditures									8.2	22.1	13.1
Depreciation and amortization, including depreciation and amortization of stock-based compensation, Gross									10.9	6.7	9.6
Corporate | Discontinued operations
Business Segment Information
Total assets	$ 108.3				$ 126.4				$ 108.3	$ 126.4	$ 129.1

Business Segment Information 71

Business Segment Information - Reconcile of Gross Profit to Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2017	May 31, 2016	May 31, 2015
Reconciliation of segment gross profit to consolidated income before provision for income taxes
Segment gross profit	$ 79.8	$ 69	$ 66.2	$ 61.5	$ 65.6	$ 59.3	$ 59.1	$ 53.9	$ 276.5	$ 237.9	$ 130.8
Selling, general and administrative									(196.7)	(173.2)	(172.4)
Earnings (Loss) from joint ventures									(0.2)	(0.3)	0.2
Loss on extinguishment of debt										(0.4)	(44.9)
Interest expense									(5.5)	(6.4)	(27.2)
Interest income									0.2	0.3	0.3
Income (Loss) from continuing operations before provision for income taxes									$ 74.3	$ 57.9	$ (113.2)

Business Segment Information 72

Business Segment Information - Sales by Product and Services (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2017	May 31, 2016	May 31, 2015
Net sales	$ 492.3	$ 446.7	$ 423.8	$ 404.8	$ 468.6	$ 412.1	$ 431.5	$ 386.7	$ 1,767.6	$ 1,698.9	$ 1,621.4
Aviation supply chain
Net sales									998.7	903.2	847.6
Maintenance, repair and overhaul services
Net sales									486.7	521.8	468.5
Expeditionary airlift services
Net sales									176.8	173.4	173.3
Mobility products
Net sales									$ 105.4	$ 100.5	$ 132

Business Segment Information 73

Business Segment Information - Geographic Data (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2017	May 31, 2016	May 31, 2015
Business Segment Information
Long-lived assets	$ 615.6				$ 574.3				$ 615.6	$ 574.3
Sales	492.3	$ 446.7	$ 423.8	$ 404.8	468.6	$ 412.1	$ 431.5	$ 386.7	1,767.6	1,698.9	$ 1,621.4
Aviation Services
Business Segment Information
Sales									1,485.4	1,425	1,316.1
Expeditionary Services
Business Segment Information
Sales									282.2	273.9	305.3
United States
Business Segment Information
Long-lived assets	452.8				489.9				452.8	489.9
Europe
Business Segment Information
Long-lived assets	122.5				73.1				122.5	73.1
Other
Business Segment Information
Long-lived assets	$ 40.3				$ 11.3				40.3	11.3
Foreign countries
Business Segment Information
Sales									$ 618.8	$ 494.6	$ 538.9
Foreign countries | Total sales | Geographic concentration
Business Segment Information
Percentage of total sales									35.00%	29.10%	33.20%
U.S. Department of Defense, other U.S. government agencies and their contractors
Business Segment Information
Sales									$ 454.8	$ 523.6	$ 495.6
Percentage of total sales									25.70%	30.80%	30.60%
U.S. Department of Defense, other U.S. government agencies and their contractors | Aviation Services
Business Segment Information
Sales									$ 260.2	$ 301.1	$ 237.3
U.S. Department of Defense, other U.S. government agencies and their contractors | Expeditionary Services
Business Segment Information
Sales									$ 194.6	$ 222.5	$ 258.3

Selected Quarterly Data (Unau74

Selected Quarterly Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2017	May 31, 2016	May 31, 2015
Sales	$ 492.3	$ 446.7	$ 423.8	$ 404.8	$ 468.6	$ 412.1	$ 431.5	$ 386.7	$ 1,767.6	$ 1,698.9	$ 1,621.4
Gross profit	79.8	69	66.2	61.5	65.6	59.3	59.1	53.9	276.5	237.9	130.8
Income (Loss) from continuing operations	15.1	13.1	12.1	9.9	11.8	9.9	9.2	7.4	50.2	38.3	(73.9)
Income (Loss) from discontinued operations	6.1	0.6		(0.4)	0.2	(5.1)	(1.2)	15.5	6.3	9.4	84.1
Net income	$ 21.2	$ 13.7	$ 12.1	$ 9.5	$ 12	$ 4.8	$ 8	$ 22.9	$ 56.5	$ 47.7	$ 10.2
Earnings (Loss) per share - basic:
Earnings (Loss) from continuing operations	$ 0.44	$ 0.39	$ 0.35	$ 0.29	$ 0.35	$ 0.29	$ 0.26	$ 0.21	$ 1.47	$ 1.10	$ (1.90)
Earnings (Loss) from discontinued operations	0.18	0.02		(0.01)		(0.15)	(0.03)	0.44	0.19	0.27	2.16
Earnings per share - basic	0.62	0.41	0.35	0.28	0.35	0.14	0.23	0.65	1.66	1.37	0.26
Earnings (Loss) per share - diluted:
Earnings (Loss) from continuing operations	0.44	0.38	0.35	0.29	0.34	0.29	0.26	0.21	1.45	1.10	(1.90)
Earnings (Loss) from discontinued operations	0.18	0.02		(0.01)		(0.15)	(0.03)	0.44	0.19	0.27	2.14
Earnings per share - diluted	$ 0.62	$ 0.40	$ 0.35	$ 0.28	$ 0.34	$ 0.14	$ 0.23	$ 0.65	$ 1.64	$ 1.37	$ 0.24
Telair Cargo Group
Earnings (Loss) per share - diluted:
Gain on sale of assets								$ 27.7

Allowance for Doubtful Accoun75

Allowance for Doubtful Accounts (Details) - Allowance for Doubtful Accounts - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Changes in allowance for doubtful accounts
Balance, beginning of year	$ 4	$ 5.8	$ 6.2
Provision charged to operations	2.4	0.3	1.7
Deductions for accounts written off, net of recoveries	(0.6)	(2.1)	(1.6)
Reclassification to assets of discontinued operations			(0.1)
Balance, end of year	$ 5.8	$ 4	5.8
Telair Cargo Group
Changes in allowance for doubtful accounts
Sale of Telair Cargo Group			$ (0.4)