COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands	3 Months Ended			6 Months Ended			12 Months Ended	20 Months Ended
	Sep. 30, 2015 USD ($) aircraft Agreements Facility	Jun. 30, 2015 aircraft	Sep. 30, 2014 USD ($) aircraft	Mar. 31, 2016 USD ($) aircraft	Sep. 30, 2015 USD ($) aircraft Agreements Facility	Sep. 30, 2014 USD ($) aircraft Agreements	Mar. 31, 2015 aircraft Employee	May. 31, 2017 USD ($)	Aug. 12, 2015 People
Commitments And Contingencies [Abstract]
Unrecorded unconditional purchase obligation, estimated deferral due in remainder of fiscal year | $	$ 100,000				$ 100,000
Unrecorded unconditional purchase obligation, estimated annual expenditures for next two fiscal years | $	100,000				100,000
Unrecorded unconditional purchase obligation, estimated annual expenditures after second fiscal year | $	$ 50,000				$ 50,000
Number of signed client contracts	11				11
Operating leases rental expense | $	$ 54,400		$ 35,400		$ 108,300	$ 68,600
Number of aircraft sale leaseback	0		14		0	14
Sale leaseback transaction, gross proceeds | $	$ 0		$ 380,700		$ 0	$ 380,700
Number of agreements to leaseback aircraft | Agreements	0				0	14
Sale Leaseback Transaction Lease Terms, Maximum					180 months
Sale Leaseback Transaction Lease Renewal Option Terms, Maximum					240 months
Number of leased aircraft	81				81
Monthly Rent payment | $					$ 13,067
Site Contingency, Number of Locations | Facility	3				3
Number Of Fatalities, Crew Members | People									2
Number Of Fatalities, Passengers | People									4
Number Of Surviving Passengers | People									6
Loss Contingency, Range of Possible Loss, Minimum | $	$ 6,000				$ 6,000
Loss Contingency, Range of Possible Loss, Maximum | $	$ 9,000				$ 9,000
Analysis Of Aircraft Orders And Options Rollforward
Aircraft Delivered	(1)		(2)		(3)	(11)
Voluntary Separation Program
Commitments And Contingencies [Abstract]
Voluntary Separation Program Number Of Employees Offered | Employee							2,888
Voluntary Separation Program Number Of Employees Acceptance | Employee							137
Severance costs | $	$ 900				$ 7,300
Voluntary Separation Program | Direct cost
Commitments And Contingencies [Abstract]
Severance costs | $					6,700
Voluntary Separation Program | General administrative expense
Commitments And Contingencies [Abstract]
Severance costs | $					600
Voluntary Separation Program | Forecast
Commitments And Contingencies [Abstract]
Severance costs | $								$ 3,500
Involuntary Separation Program
Commitments And Contingencies [Abstract]
Severance costs | $	4,800				6,400
Involuntary Separation Program | Direct cost
Commitments And Contingencies [Abstract]
Severance costs | $	2,000				2,500
Involuntary Separation Program | General administrative expense
Commitments And Contingencies [Abstract]
Severance costs | $	$ 2,800				$ 3,900
Involuntary Separation Program | Forecast
Commitments And Contingencies [Abstract]
Severance costs | $				$ 5,500
Unionized Employees Concentration Risk | Workforce Subject to Collective Bargaining Arrangements
Commitments And Contingencies [Abstract]
Concentration Risk, Percentage					49.00%
Collective Bargaining Agreements, Maximum Annual Escalation Per Employee, Percent					21.00%
Unionized Employees Concentration Risk | Workforce Subject to Collective Bargaining Arrangements Expiring within One Year
Commitments And Contingencies [Abstract]
Concentration Risk, Percentage					6.00%
Six months ending March 31, 2016 to fiscal year 2017
Commitments And Contingencies [Abstract]
Number of leased aircraft	9				9
Monthly Rent payment | $					$ 1,070
FY2018 to FY2020
Commitments And Contingencies [Abstract]
Number of leased aircraft	47				47
Monthly Rent payment | $					$ 9,255
FY2021 to FY2024
Commitments And Contingencies [Abstract]
Number of leased aircraft	25				25
Monthly Rent payment | $					$ 2,742
Medium aircraft
Analysis Of Aircraft Orders And Options Rollforward
Aircraft Delivered	0		0		(1)	(3)
Large aircraft
Analysis Of Aircraft Orders And Options Rollforward
Aircraft Delivered	(1)		(2)		(2)	(8)
Aircraft
Commitments And Contingencies [Abstract]
Operating leases rental expense | $	$ 47,300		$ 28,500		$ 93,900	$ 54,900
Commitments
Commitments And Contingencies [Abstract]
Number of contingent aircraft	17				17
Analysis Of Aircraft Orders And Options Rollforward
Beginning of quarter	46	45		41	45
Aircraft Delivered	(1)	(2)
Aircraft ordered	0	0
Exercised options	0	3
Expired options	0	0
Reclassification	(4)	0
End of quarter	41	46			41		45
Options
Analysis Of Aircraft Orders And Options Rollforward
Beginning of quarter	21	30		21	30
Aircraft Delivered	0	0
Aircraft ordered	0	0
Exercised options	0	(3)
Expired options	(4)	(6)
Reclassification	4	0
End of quarter	21	21			21		30
Other Commitments
Commitments And Contingencies [Abstract]
Purchase commitments | $	$ 395,700				$ 395,700
Aircraft
Commitments And Contingencies [Abstract]
Number of aircraft purchase commitments, due remainder of fiscal year	20				20
Number of aircraft purchase commitments, due in two years	8				8
Number of aircraft purchase commitments, due in three years	6				6
Number of aircraft purchase commitments, due in four years	4				4
Number of aircraft purchase commitments, due in five years and after	3				3
Number of aircraft purchase commitments	41				41
Purchase commitments, due remainder of year | $	$ 251,973				$ 251,973
Purchase commitments, Due within Two Years | $	135,632				135,632
Purchase commitments, Due within Three Years | $	78,778				78,778
Purchase commitments, Due within Four Years | $	58,945				58,945
Purchase commitments, Due within Five Years And After | $	31,550				31,550
Purchase commitments | $	$ 556,878				$ 556,878
Number of aircraft purchase options, due remainder of fiscal year	0				0
Number of aircraft purchase options, due in two years	5				5
Number of aircraft purchase options, due in three years	16				16
Number of aircraft purchase options, due in four years	0				0
Number of aircraft purchase options, due in five years and after	0				0
Number of aircraft purchase options	21				21
Aircraft purchase options, due remainder of year | $	$ 26,291				$ 26,291
Aircraft purchase options, due in two years | $	180,100				180,100
Aircraft purchase options, due in three years | $	214,008				214,008
Aircraft purchase options, due in four years | $	0				0
Aircraft purchase options, due in five years and after | $	0				0
Aircraft purchase options | $	$ 420,399				$ 420,399
Aircraft | Medium aircraft
Commitments And Contingencies [Abstract]
Number of aircraft purchase commitments, due remainder of fiscal year	10				10
Number of aircraft purchase commitments, due in two years	0				0
Number of aircraft purchase commitments, due in three years	0				0
Number of aircraft purchase commitments, due in four years	0				0
Number of aircraft purchase commitments, due in five years and after	0				0
Number of aircraft purchase commitments	10				10
Number of aircraft purchase options, due remainder of fiscal year	0				0
Number of aircraft purchase options, due in two years	1				1
Number of aircraft purchase options, due in three years	7				7
Number of aircraft purchase options, due in four years	0				0
Number of aircraft purchase options, due in five years and after	0				0
Number of aircraft purchase options	8				8
Aircraft | Large aircraft
Commitments And Contingencies [Abstract]
Number of aircraft purchase commitments, due remainder of fiscal year	3				3
Number of aircraft purchase commitments, due in two years	4				4
Number of aircraft purchase commitments, due in three years	6				6
Number of aircraft purchase commitments, due in four years	4				4
Number of aircraft purchase commitments, due in five years and after	3				3
Number of aircraft purchase commitments	20				20
Number of aircraft purchase options, due remainder of fiscal year	0				0
Number of aircraft purchase options, due in two years	4				4
Number of aircraft purchase options, due in three years	9				9
Number of aircraft purchase options, due in four years	0				0
Number of aircraft purchase options, due in five years and after	0				0
Number of aircraft purchase options	13				13
Aircraft | Medium and Large Aircrafts
Commitments And Contingencies [Abstract]
Purchase commitments, due remainder of year | $	$ 116,662				$ 116,662
Purchase commitments, Due within Two Years | $	77,204				77,204
Purchase commitments, Due within Three Years | $	78,778				78,778
Purchase commitments, Due within Four Years | $	58,945				58,945
Purchase commitments, Due within Five Years And After | $	31,550				31,550
Purchase commitments | $	$ 363,139				$ 363,139
Aircraft | U.K. SAR configured aircraft
Commitments And Contingencies [Abstract]
Number of aircraft purchase commitments, due remainder of fiscal year	6				6
Number of aircraft purchase commitments, due in two years	4				4
Number of aircraft purchase commitments, due in three years	0				0
Number of aircraft purchase commitments, due in four years	0				0
Number of aircraft purchase commitments, due in five years and after	0				0
Number of aircraft purchase commitments	10				10
Purchase commitments, due remainder of year | $	$ 109,052				$ 109,052
Purchase commitments, Due within Two Years | $	58,428				58,428
Purchase commitments, Due within Three Years | $	0				0
Purchase commitments, Due within Four Years | $	0				0
Purchase commitments, Due within Five Years And After | $	0				0
Purchase commitments | $	$ 167,480				$ 167,480
Aircraft | Other SAR configured aircraft
Commitments And Contingencies [Abstract]
Number of aircraft purchase commitments, due remainder of fiscal year	1				1
Number of aircraft purchase commitments, due in two years	0				0
Number of aircraft purchase commitments, due in three years	0				0
Number of aircraft purchase commitments, due in four years	0				0
Number of aircraft purchase commitments, due in five years and after	0				0
Number of aircraft purchase commitments	1				1
Purchase commitments, due remainder of year | $	$ 26,259				$ 26,259
Purchase commitments, Due within Two Years | $	0				0
Purchase commitments, Due within Three Years | $	0				0
Purchase commitments, Due within Four Years | $	0				0
Purchase commitments, Due within Five Years And After | $	0				0
Purchase commitments | $	$ 26,259				$ 26,259