LEASES Narrative (Details) $ in Thousands		3 Months Ended				6 Months Ended
	Oct. 03, 2019 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($) aircraft	Jun. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) aircraft	Sep. 30, 2018 USD ($)
Lessee, Lease, Description [Line Items]
Operating leases rental expense			$ 38,300		$ 49,600	$ 90,400	$ 99,700
Short-term Lease, Cost			$ 300			$ 600
Property Subject to or Available for Operating Lease, Number of Units | aircraft			49			49
Liabilities Subject to Compromise, Number Of Aircraft Lease Rejections | aircraft			10			10
Debtor Reorganization Items, Net Gain (Loss) on Rejection of Leases and Other Executory Contracts			$ (4,170)			$ (30,221)
S-76C Aircraft
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Number Of Aircraft Lease Rejections | aircraft			9			9
H225 Aircraft
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Number Of Aircraft Lease Rejections | aircraft			4			4
Debtor Reorganization Items, Net Gain (Loss) on Rejection of Leases and Other Executory Contracts						$ 4,300
Lease Rejections, Reduction In Rights Of Use Assets						11,900
Lease Rejections, Reduction in Operating Lease Liabilities						$ 12,400
S-76D Aircraft
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Number Of Aircraft Lease Rejections | aircraft			1			1
S-76s [Member]
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Number Of Aircraft Lease Rejections | aircraft			10			10
Debtor Reorganization Items, Net Gain (Loss) on Rejection of Leases and Other Executory Contracts			$ 4,200	$ 26,000
Lease Rejections, Reduction In Rights Of Use Assets						$ 18,600
Lease Rejections, Reduction in Operating Lease Liabilities						20,200
S-76s [Member] | Subsequent Event [Member]
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Payments under Bankruptcy Court Order for Resolutions of Contingencies Subject to Chapter 11	$ 3,900
Milestone Omnibus Agreement [Member]
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Early Contract Termination Fees			20,063			20,063
Milestone Omnibus Agreement [Member] | Accounts Payable and Accrued Liabilities [Member] | H225 Aircraft
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Early Contract Termination Fees			2,800			2,800
Milestone Omnibus Agreement [Member] | Commitments [Member] | H225 Aircraft
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Early Contract Termination Fees			9,700			9,700
Milestone Omnibus Agreement [Member] | Debt [Member] | H225 Aircraft
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Early Contract Termination Fees			9,400			9,400
VIH Aviation Group [Member] | Leasing From Related Party [Member]
Lessee, Lease, Description [Line Items]
Related party transaction, expenses from transactions with related party			$ 3,000		4,500	$ 7,500	9,500
VIH Aviation Group [Member] | Leasing From Related Party [Member] | S-92 [Member]
Lessee, Lease, Description [Line Items]
Property Subject to or Available for Operating Lease, Number of Units | aircraft			6			6
VIH Aviation Group [Member] | Leasing From Related Party [Member] | AW139 [Member]
Lessee, Lease, Description [Line Items]
Property Subject to or Available for Operating Lease, Number of Units | aircraft			1			1
VIH Helicopters USA, Inc [Member] | Leasing From Related Party [Member]
Lessee, Lease, Description [Line Items]
Related party transaction, expenses from transactions with related party			$ 100		100	$ 100	100
Aircraft
Lessee, Lease, Description [Line Items]
Operating leases rental expense			$ 32,800		$ 43,200	$ 79,300	$ 87,300
Aircraft Type Lease Arrangement [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract			180 months			180 months
Lessee, Operating Lease, Renewal Term			240 months			240 months
Other Operating Lease Arrangement [Member]
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Early Contract Termination Fees			$ 5,300			$ 5,300
Lease Rejections, Reduction In Rights Of Use Assets			13,200
Lease Rejections, Reduction in Operating Lease Liabilities			$ 18,900
Other Operating Lease Arrangement [Member] | Subsequent Event [Member]
Lessee, Lease, Description [Line Items]
Liabilities Subject to Compromise, Payments under Bankruptcy Court Order for Resolutions of Contingencies Subject to Chapter 11		$ 600