TotalOff-Network and Other Revenues increased by $11.1 million, or 24 percent, to $57.3 million, as compared to the three months ended March 31, 2018 due to the following:
| • | | Transponder, MSS and otherOff-Network services revenues increased by an aggregate of $14.9 million to $49.9 million, inclusive of $14.3 million in revenue recognized in the first quarter of 2019 from a network services customer as a result of the adoption of ASC 842, with no comparable amount in the first quarter of 2018. |
| • | | Satellite-related services reported a decrease of $3.8 million, to $7.4 million, due to the completion of a contract for professional services supporting third-party satellite operations in the first quarter of 2018 with no similar contracts completed in the first quarter of 2019. |
For the three months ended March 31, 2019, changes in operating expenses, interest expense, net, and other significant income statement items are described below.
Direct costs of revenue (excluding depreciation and amortization) increased by $22.8 million, or 28 percent, to $105.4 million for the three months ended March 31, 2019, as compared to the three months ended March 31, 2018. The increase was primarily due to $16.1 million in equipment and third-party service costs recognized in the first quarter of 2019 under ASC 842 and $6.8 million in costs related to the entry into service of twonon-capex satellites in January 2019, with no comparable amounts in the first quarter of 2018.
Selling, general and administrative expenses decreased by $8.6 million, or 14 percent, to $51.7 million for the three months ended March 31, 2019, as compared to the three months ended March 31, 2018. The decrease was primarily due to a $10.3 million decline in professional fees, largely due to costs incurred in the first quarter of 2018 relating to liability management activities with no comparable amounts in 2019, partially offset by an increase of $2.8 million in staff-related expenses.
Depreciation and amortization expense increased by $4.6 million, or 3 percent, to $171.1 million for the three months ended March 31, 2019, as compared to the three months ended March 31, 2018.
Interest expense, net consists of the gross interest expense we incur, together with gains and losses on interest rate cap contracts (which reflect the change in their fair value), offset by interest income earned and the amount of interest we capitalize related to assets under construction. As of March 31, 2019, we held interest rate cap contracts with an aggregate notional amount of $2.4 billion to mitigate the risk of interest rate expense increase on the floating-rate term loans under our senior secured credit facilities. The contracts have not been designated as hedges for accounting purposes.
Interest expense, net increased by $34.1 million, or 12 percent, to $316.6 million for the three months ended March 31, 2019, as compared to $282.5 million in the three months ended March 31, 2018. The increase was principally due to:
| • | | an increase of $30.1 million corresponding to the decrease in fair value of the interest rate cap contracts; |
| • | | an increase of $3.9 million from lower capitalized interest primarily resulting from decreased levels of satellites and related assets under construction; and |
| • | | a net increase of $2.0 million in interest expense primarily resulting from our refinancing activities in 2018. |
Thenon-cash portion of total interest expense, net was $47.4 million for the three months ended March 31, 2019, primarily consisting of interest expense related to the significant financing component identified in our customer contracts, amortization and accretion of discounts and premiums, the loss resulting from the decrease in fair value of the interest rate cap contracts we hold and amortization of deferred financing fees.
Other income, netwas $1.4 million for the three months ended March 31, 2019, as compared to other income, net of $4.4 million for the three months ended March 31, 2018. The decrease of $3.0 million was primarily due to $3.1 million of other lease income recognized in the three months ended March 31, 2018 with no comparable amount in 2019.