BASIS OF PRESENTATION, CONSOLIDATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment Disposed of and Impairments (Details) $ in Thousands	3 Months Ended
	Jun. 30, 2018 USD ($) aircraft	Jun. 30, 2017 USD ($) aircraft
Property, Plant and Equipment [Line Items]
Number of aircraft sold or disposed of | aircraft	3	6
Proceeds from asset dispositions	$ 7,774	$ 41,975
Gain (loss) on disposal of assets	$ (1,678)	$ 699
Number of aircraft impaired | aircraft	0	2
Impairment charges on aircraft held for sale	$ 0	$ 1,564
Air transportation equipment
Property, Plant and Equipment [Line Items]
Gain (loss) on disposal of assets	$ (1,678)	$ 2,263