COMMITMENTS AND CONTINGENCIES Operating Leases (Details) $ in Thousands	12 Months Ended
	Mar. 31, 2019 USD ($) aircraft	Mar. 31, 2018 USD ($) aircraft	Mar. 31, 2017 USD ($)
Operating Leased Assets [Line Items]
Operating Leases, Rent Expense, Net	$ 192,300	$ 208,700	$ 212,600
Property Subject to or Available for Operating Lease, Number of Units | aircraft	75
Operating Leases, Future Minimum Payments Due, Rolling Maturity [Abstract]
Operating leases, future minimum payments, due 2019	$ 132,883
Operating leases, future minimum payments, due 2020	69,813
Operating leases, future minimum payments, due 2021	47,832
Operating leases, future minimum payments, due 2022	25,001
Operating leases, future minimum payments, due 2023	13,599
Operating leases, future minimum payments, due thereafter	29,256
Operating leases, future minimum payments, total	$ 318,384
Number Of Aircraft Sale Leaseback | aircraft	0	0
Sale Leaseback Transaction, Gross Proceeds, Investing Activities	$ 0	$ 0
Lessor, Operating Lease, Term of Contract	180 months
Lessor, Operating Lease, Renewal Term	240 months
Fiscal Year 2020 To Fiscal Year 2021
Operating Leased Assets [Line Items]
Property Subject to or Available for Operating Lease, Number of Units | aircraft	43
Fiscal Year 2022 To Fiscal Year 2024
Operating Leased Assets [Line Items]
Property Subject to or Available for Operating Lease, Number of Units | aircraft	32
Operating Lease | Aircraft
Operating Leased Assets [Line Items]
Operating Leases, Rent Expense, Net	$ 169,200	$ 181,300	$ 188,200
Operating Leases, Future Minimum Payments Due, Rolling Maturity [Abstract]
Operating leases, future minimum payments, due 2019	121,516
Operating leases, future minimum payments, due 2020	59,999
Operating leases, future minimum payments, due 2021	39,035
Operating leases, future minimum payments, due 2022	16,605
Operating leases, future minimum payments, due 2023	5,086
Operating leases, future minimum payments, due thereafter	0
Operating leases, future minimum payments, total	242,241
Operating Lease | Other
Operating Leases, Future Minimum Payments Due, Rolling Maturity [Abstract]
Operating leases, future minimum payments, due 2019	11,367
Operating leases, future minimum payments, due 2020	9,814
Operating leases, future minimum payments, due 2021	8,797
Operating leases, future minimum payments, due 2022	8,396
Operating leases, future minimum payments, due 2023	8,513
Operating leases, future minimum payments, due thereafter	29,256
Operating leases, future minimum payments, total	$ 76,143