FINANCING ACTIVITIES (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

(in millions)	December 31, 2020		December 31, 2019
737 Aircraft Notes payable through April 2020	$	—	$	20
Term Loan Agreement payable through May 2020 - 5.223%	—		134
2.65% Notes due November 2020	—		500
2.75% Notes due 2022	300		300
Pass Through Certificates due 2022 - 6.24%	137		197
4.75% Notes due 2023	1,250		—
1.25% Convertible Notes due 2025	1,945		—
5.25% Notes due 2025	1,550		—
Term Loan Agreement payable through 2025 - 1.65%	119		—
3.00% Notes due 2026	300		300
Term Loan Agreement payable through 2026 - 1.34%	159		178
3.45% Notes due 2027	300		300
5.125% Notes due 2027	2,000		—
7.375% Debentures due 2027	119		122
Term Loan Agreement payable through 2028 - 1.65%	184		—
2.625% Notes due 2030	500		—
1.000% Payroll Support Program Loan due 2030 (See Note 2)	976		—
Finance leases	542		627
	$	10,381	$	2,678
Less current maturities	220		819
Less debt discount and issuance costs	50		13
	$	10,111	$	1,846