LEASES MATURITIES OF LEASE LIABILITIES (Details) $ in Millions	Sep. 30, 2019 USD ($)
Aircraft [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 63
Lessee, Operating Lease, Liability, Payments, Due Year Two	234
Lessee, Operating Lease, Liability, Payments, Due Year Three	196
Lessee, Operating Lease, Liability, Payments, Due Year Four	171
Lessee, Operating Lease, Liability, Payments, Due Year Five	116
Lessee, Operating Lease, Liability, Payments, Due after Year Five	330
Lessee, Operating Lease, Liability, Payments, Due	1,110
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(140)
Operating Lease, Liability	970
CPA Aircraft [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	20
Lessee, Operating Lease, Liability, Payments, Due Year Two	79
Lessee, Operating Lease, Liability, Payments, Due Year Three	79
Lessee, Operating Lease, Liability, Payments, Due Year Four	79
Lessee, Operating Lease, Liability, Payments, Due Year Five	79
Lessee, Operating Lease, Liability, Payments, Due after Year Five	408
Lessee, Operating Lease, Liability, Payments, Due	744
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(135)
Operating Lease, Liability	609
Airport Facilities [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	1
Lessee, Operating Lease, Liability, Payments, Due Year Two	3
Lessee, Operating Lease, Liability, Payments, Due Year Three	3
Lessee, Operating Lease, Liability, Payments, Due Year Four	2
Lessee, Operating Lease, Liability, Payments, Due Year Five	2
Lessee, Operating Lease, Liability, Payments, Due after Year Five	12
Lessee, Operating Lease, Liability, Payments, Due	23
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(4)
Operating Lease, Liability	19
Corporate real estate [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	2
Lessee, Operating Lease, Liability, Payments, Due Year Two	7
Lessee, Operating Lease, Liability, Payments, Due Year Three	6
Lessee, Operating Lease, Liability, Payments, Due Year Four	4
Lessee, Operating Lease, Liability, Payments, Due Year Five	4
Lessee, Operating Lease, Liability, Payments, Due after Year Five	77
Lessee, Operating Lease, Liability, Payments, Due	100
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(54)
Operating Lease, Liability	$ 46