COMMITMENTS AND CONTINGENCIES Aircraft Purchase Contracts (Details) $ in Thousands		3 Months Ended	12 Months Ended
	May 01, 2019 USD ($) aircraft	Sep. 30, 2019 aircraft	Mar. 31, 2019 USD ($) aircraft	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation, Writedown Of Future Commitments | $			$ 17,500
Contract termination costs | $			(14,699)	$ 0	$ 0
H175 [Member] | Aircraft Purchase Amendment [Member] | Subsequent Event [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded unconditional purchase obligation minimum quantity required, due in year three | aircraft	3
Unrecorded unconditional purchase obligation, minimum quantity required | aircraft	22
Contract Postponement Period	18 months
Capital expenditure deferral | $	$ 110,000
Increase (Decrease) In Purchase Obligation | $	$ 18,400
Other commitments
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded unconditional purchase obligation | $			$ 37,800
Aircraft | Subsequent Event [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded unconditional purchase obligation minimum quantity required, due in one year | aircraft	4
Unrecorded unconditional purchase obligation minimum quantity required, due in year two | aircraft	0
Unrecorded unconditional purchase obligation minimum quantity required, due in year three | aircraft	3
Unrecorded unconditional purchase obligation minimum quantity required, due in year four and thereafter | aircraft	19
Unrecorded unconditional purchase obligation, minimum quantity required | aircraft	26
Unrecorded unconditional purchase obligation, due within one year | $	$ 62,319
Unrecorded unconditional purchase obligation, due within two years | $	10,542
Unrecorded unconditional purchase obligation, due within three years | $	59,808
Unrecorded unconditional purchase obligation, due within four years and thereafter | $	311,027
Unrecorded unconditional purchase obligation | $	$ 443,696
Aircraft | Large Aircraft | Subsequent Event [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded unconditional purchase obligation minimum quantity required, due in one year | aircraft	0
Unrecorded unconditional purchase obligation minimum quantity required, due in year two | aircraft	0
Unrecorded unconditional purchase obligation minimum quantity required, due in year three | aircraft	3
Unrecorded unconditional purchase obligation minimum quantity required, due in year four and thereafter | aircraft	19
Unrecorded unconditional purchase obligation, minimum quantity required | aircraft	22
Bankruptcy Claims, Number of Claims on Material Contracts Rejected | aircraft		22
Aircraft | Medium And Large [Member] | Subsequent Event [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded unconditional purchase obligation, due within one year | $	$ 3,437
Unrecorded unconditional purchase obligation, due within two years | $	10,542
Unrecorded unconditional purchase obligation, due within three years | $	59,808
Unrecorded unconditional purchase obligation, due within four years and thereafter | $	311,027
Unrecorded unconditional purchase obligation | $	$ 384,814
Aircraft | U.K. SAR Configured Aircraft [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number Of Leased Aircraft | aircraft			4
Aircraft | U.K. SAR Configured Aircraft [Member] | Subsequent Event [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded unconditional purchase obligation minimum quantity required, due in one year | aircraft	4
Unrecorded unconditional purchase obligation minimum quantity required, due in year two | aircraft	0
Unrecorded unconditional purchase obligation minimum quantity required, due in year three | aircraft	0
Unrecorded unconditional purchase obligation minimum quantity required, due in year four and thereafter | aircraft	0
Unrecorded unconditional purchase obligation, minimum quantity required | aircraft	4
Unrecorded unconditional purchase obligation, due within one year | $	$ 58,882
Unrecorded unconditional purchase obligation, due within two years | $	0
Unrecorded unconditional purchase obligation, due within three years | $	0
Unrecorded unconditional purchase obligation, due within four years and thereafter | $	0
Unrecorded unconditional purchase obligation | $	$ 58,882
Number Of Aircraft Purchased | aircraft		1
Cancellable commitments | Subsequent Event [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded unconditional purchase obligation, minimum quantity required | aircraft	5
Unrecorded unconditional purchase obligation | $	$ 94,100
Deposits | $	$ 4,500
Cancellable commitments | H175 [Member] | Aircraft Purchase Amendment [Member] | Subsequent Event [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded unconditional purchase obligation, minimum quantity required | aircraft	5