LEASES - Schedule of Leased Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	$ 1,400	$ 1,711
Operating Lease, Expense	602	668
Sublease Income	(14)	(13)
Lease, Cost	588	655
Aircraft Leases [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	750	1,049
Operating Lease, Cost	215	246
CPA Aircraft [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	579	596
Operating Lease, Cost	80	79
Airport Facilities [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	16	18
Operating Lease, Cost	288	324
Corporate real estate [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	55	48
Operating Lease, Cost	$ 19	$ 19