COMMITMENTS (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) aircraft carriers	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) aircraft carriers	Jun. 30, 2015 USD ($)
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Rent Expense	$ 63	$ 67	$ 144	$ 140
Capacity purchase arrangements (carriers) | carriers	3		3
Aircraft Commitments [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Remainder of 2016	$ 305		$ 305
2017	931		931
2018	725		725
2019	648		648
2020	337		337
Thereafter	400		400
Total	3,346		3,346
Capacity Purchase Agreements [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Remainder of 2016	34		34
2017	78		78
2018	81		81
2019	86		86
2020	92		92
Thereafter	745		745
Total	1,116		1,116
Aircraft [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Remainder of 2016	39		39
2017	99		99
2018	90		90
2019	82		82
2020	73		73
Thereafter	400		400
Total	783		783
Facility Leases [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Remainder of 2016	47		47
2017	90		90
2018	42		42
2019	41		41
2020	40		40
Thereafter	142		142
Total	$ 402		$ 402
B-737 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of lease contracts (aircraft) | aircraft	21		21
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Committed to Purchase (in Aircraft) | aircraft	56		56
Options to Purchase Additional (in Aircraft) | aircraft	46		46
B737-900ER [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Committed to Purchase (in Aircraft) | aircraft	19		19
B737 MAX [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Committed to Purchase (in Aircraft) | aircraft	37		37
Q400 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of lease contracts (aircraft) | aircraft	15		15
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Committed to Purchase (in Aircraft) | aircraft	2		2
Unrecorded Unconditional Purchase Obligation, Not Intended to Take Delivery | aircraft	2		2
Options to Purchase Additional (in Aircraft) | aircraft	5		5
E175 [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Committed to Purchase (in Aircraft) | aircraft	33		33
Options to Purchase Additional (in Aircraft) | aircraft	30		30
Horizon [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Capacity purchase arrangements	100.00%		100.00%
Capacity Purchase Agreement with SkyWest [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of lease contracts (aircraft) | aircraft	15		15
Capacity Purchase Agreement with SkyWest [Member] | CRJ-700 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of lease contracts (aircraft) | aircraft	6		6
Capacity Purchase Agreement with SkyWest [Member] | E175 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of lease contracts (aircraft) | aircraft	9		9
Number of optional additional leases (aircraft) | aircraft	8		8