COMMITMENTS AND CONTINGENCIES COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) aircraft carriers	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Rent expense	$ 315	$ 295	$ 288
Capacity purchase arrangements, Carriers | carriers	3
Horizon [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Capacity purchase arrangements, Percent	100.00%
Aircraft Commitments [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	$ 926
2018	848
2019	694
2020	354
2021	277
Thereafter	361
Total	3,460
Capacity Purchase Agreements[Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	76
2018	80
2019	85
2020	90
2021	94
Thereafter	676
Total	1,101
Aircraft Leases [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2017	302
2018	316
2019	305
2020	279
2021	242
Thereafter	953
Total	2,397
Facility Leases [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2017	123
2018	73
2019	63
2020	57
2021	50
Thereafter	171
Total	$ 537
B-737 [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Commited to purchase (in aircraft) | aircraft	54
Option to purchase additional (in aircraft) | aircraft	41
A-320-Neo [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Option to purchase additional (in aircraft) | aircraft	30
B737-900ER [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Commited to purchase (in aircraft) | aircraft	22
B737 MAX [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Commited to purchase (in aircraft) | aircraft	32
Q400 [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Commited to purchase (in aircraft) | aircraft	33
E-175 [Domain]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Option to purchase additional (in aircraft) | aircraft	30
Property Subject to Operating Lease [Member] | B-737 [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Operating leases, number of leased assets (in aircraft) | aircraft	17
Property Subject to Operating Lease [Member] | Q400 [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Operating leases, number of leased assets (in aircraft) | aircraft	15
Property Subject to Operating Lease [Member] | Airbus [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Operating leases, number of leased assets (in aircraft) | aircraft	53
Property Subject to Operating Lease [Member] | E-175 [Domain]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Operating leases, number of leased assets (in aircraft) | aircraft	15
Property Available for Operating Lease [Member] | A321neo [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Property Subject to or Available for Operating Lease, Number of Optional Additional Units | aircraft	10
Capacity Purchase Agreement with SkyWest [Member] | E175 [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Property Subject to or Available for Operating Lease, Number of Optional Additional Units | aircraft	8
Capacity Purchase Agreement with SkyWest [Member] | Property Available for Operating Lease [Member] | E-175 [Domain]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Property Subject to or Available for Operating Lease, Number of Optional Additional Units | aircraft	5
Aircraft Maintenance Deposits [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Other Commitment, Due after Fifth Year	$ 90
Other Commitment, Due in Fifth Year	63
Other Commitment, Due in Fourth Year	68
Other Commitment, Due in Third Year	65
Other Commitment, Due in Second Year	61
Other Commitment, Due in Next Twelve Months	59
Other Commitment	406
Aircraft Maintenance and Parts Management [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Other Commitment, Due after Fifth Year	0
Other Commitment, Due in Fifth Year	40
Other Commitment, Due in Fourth Year	37
Other Commitment, Due in Third Year	35
Other Commitment, Due in Second Year	32
Other Commitment, Due in Next Twelve Months	30
Other Commitment	$ 174