COMMITMENTS AND CONTINGENCIES Long-term Purchase Commitments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) aircraft
Long-term Purchase Commitment [Line Items]
Additional Options	6
Additional - Pre Owned 700 A/C (in units)	2
Conversion - 737 NG 700 to 737 NG 800 firm orders	25
Additional 737 NG 800 Options	33
Options - 737NG (in units)	18
Additional - 700 A/C (in units)	35	[1]
Options - 737MAX (in units)	191
Total	533
Firm - 737NG 800 (in units)	89
Firm - 737MAX (in units)	30
Firm - 738MAX (in units)	170	[2]
2016
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	17
Options - 737MAX (in units)	0
Total	53
Firm - 737NG 800 (in units)	36
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	0
2017
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	14
Options - 737MAX (in units)	0
Total	63
Firm - 737NG 800 (in units)	35
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	14
2018
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	18
Additional - 700 A/C (in units)	4
Options - 737MAX (in units)	0
Total	53
Firm - 737NG 800 (in units)	18
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	13
2019
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Options - 737MAX (in units)	0
Total	25
Firm - 737NG 800 (in units)	0
Firm - 737MAX (in units)	15
Firm - 738MAX (in units)	10
2020
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Options - 737MAX (in units)	0
Total	36
Firm - 737NG 800 (in units)	0
Firm - 737MAX (in units)	14
Firm - 738MAX (in units)	22
2021
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Options - 737MAX (in units)	18
Total	52
Firm - 737NG 800 (in units)	0
Firm - 737MAX (in units)	1
Firm - 738MAX (in units)	33
2022
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Options - 737MAX (in units)	19
Total	49
Firm - 737NG 800 (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	30
2023
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Options - 737MAX (in units)	23
Total	47
Firm - 737NG 800 (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	24
2024
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Options - 737MAX (in units)	23
Total	47
Firm - 737NG 800 (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	24
2025
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Options - 737MAX (in units)	36
Total	36
Firm - 737NG 800 (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	0
2026
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Options - 737MAX (in units)	36
Total	36
Firm - 737NG 800 (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	0
2027
Long-term Purchase Commitment [Line Items]
Options - 737NG (in units)	0
Additional - 700 A/C (in units)	0
Options - 737MAX (in units)	36
Total	36
Firm - 737NG 800 (in units)	0
Firm - 737MAX (in units)	0
Firm - 738MAX (in units)	0
Aircraft [Member]
Long-term Purchase Commitment [Line Items]
Committed expenditures, 2016 | $	$ 1,100
Committed expenditures, 2017 | $	1,300
Committed expenditures, 2018 | $	1,100
Committed expenditures, 2019 | $	1,200
Committed expenditures, 2020 | $	1,500
Committed expenditures, 2021 and beyond | $	$ 4,400
B-737-800
Long-term Purchase Commitment [Line Items]
Number of Aircrafts Purchased	19
B-737-700
Long-term Purchase Commitment [Line Items]
Number of Aircrafts Purchased	8
Number of aircrafts leased	16
B737-300
Long-term Purchase Commitment [Line Items]
Number of aircrafts retired from service	2
B737-500
Long-term Purchase Commitment [Line Items]
Number of aircrafts retired from service	2

[1] To be acquired in leases from various third parties.

[2] The Company has flexibility to substitute MAX 7 in lieu of MAX 8 firm orders beginning in 2019.