COMMITMENTS AND CONTINGENCIES - Schedule of Purchase Commitment and Commitment Expenditures (Details) - Aircraft $ in Thousands	3 Months Ended
	Sep. 30, 2019 aircraft	Jul. 25, 2019 USD ($) aircraft	Jun. 30, 2019 USD ($) aircraft	Mar. 31, 2019 aircraft
Number of Aircraft Unconditional Commitments
Nine Months Ending March 31, 2020			3
2020			1
2021			3
2022			4
2023 and thereafter			15
Purchase Commitment - Total Aircrafts			26
Commitment Expenditures
Nine Months Ending March 31, 2020 | $			$ 63,543
2020 | $			10,692
2021 | $			60,657
2022 | $			77,428
2023 and thereafter | $			238,017
Purchase Commitments - Total | $			$ 450,337
Large
Number of Aircraft Unconditional Commitments
Nine Months Ending March 31, 2020			0
2020			0
2021			3
2022			4
2023 and thereafter			15
Purchase Commitment - Total Aircrafts			22
Commitment Expenditures
Nine Months Ending March 31, 2020 | $			$ 3,486
2020 | $			10,692
2021 | $			60,657
2022 | $			77,428
2023 and thereafter | $			238,017
Purchase Commitments - Total | $			$ 390,280
U.K. SAR
Number of Aircraft Unconditional Commitments
Nine Months Ending March 31, 2020			3
2020			1
2021			0
2022			0
2023 and thereafter			0
Purchase Commitment - Total Aircrafts			4
Commitment Expenditures
Nine Months Ending March 31, 2020 | $			$ 60,057
2020 | $			0
2021 | $			0
2022 | $			0
2023 and thereafter | $			0
Purchase Commitments - Total | $			$ 60,057
Number of leased aircraft				4
Subsequent Event [Member] | Large
Commitment Expenditures
Bankruptcy Claims, Number of Claims on Material Contracts Rejected	22
Subsequent Event [Member] | U.K. SAR
Number of Aircraft Unconditional Commitments
Purchase Commitment - Total Aircrafts		4
Commitment Expenditures
Postponement Of Commitments, Number of Aircraft		3
Capital expenditure deferral | $		$ 15,000
Number Of Aircraft Purchased	1