Special Charges (Credits) - Narrative (Details)	3 Months Ended			6 Months Ended
	Jun. 30, 2021 USD ($) aircraft	Mar. 31, 2021 USD ($) employee	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) employee aircraft	Jun. 30, 2020 USD ($)	Apr. 21, 2021 USD ($)	Feb. 28, 2021 aircraft
Restructuring Cost and Reserve [Line Items]
Government assistance received			$ 4,500,000,000	$ 5,800,000,000	$ 4,500,000,000
Government assistance received through unsecured loans			1,300,000,000	1,700,000,000	1,300,000,000
Government assistance received through grants			3,200,000,000		3,200,000,000
Issuance of warrants			57,000,000		57,000,000
Impairment of assets	$ 59,000,000		80,000,000	$ 59,000,000	130,000,000
Number of impaired aircraft | aircraft	64			64
Number of aircraft temporarily removed | aircraft							52
Severance and benefit costs	$ 11,000,000		63,000,000	$ 428,000,000	63,000,000
Total net other charges	61,000,000			77,000,000
Nonoperating unrealized gains	147,000,000		9,000,000	125,000,000	(310,000,000)
Nonoperating debt extinguishment and modification fees	62,000,000		0	62,000,000	0
CARES Act grant	(1,079,000,000)		(1,589,000,000)	(2,889,000,000)	(1,589,000,000)
Gain for the change in fair value of certain derivative assets					24,000,000
Settlement loss	0		231,000,000	46,000,000	231,000,000
Nonoperating credit loss on BRW Term Loan and related guarantee	0		0	0	697,000,000
Payroll Support Program 2 (PSP2) Warrants
Restructuring Cost and Reserve [Line Items]
Issuance of warrants				52,000,000
PSP3 Warrants
Restructuring Cost and Reserve [Line Items]
Issuance of warrants				99,000,000
PSP2 Note
Restructuring Cost and Reserve [Line Items]
Government assistance received through grants				1,100,000,000
PSP3 Note
Restructuring Cost and Reserve [Line Items]
Government assistance received through grants				(2,900,000,000)
Deferred grant income	1,100,000,000			1,100,000,000
2026 Notes and 2029 Notes | Secured Debt
Restructuring Cost and Reserve [Line Items]
Face amount	4,000,000,000.0			4,000,000,000.0		$ 4,000,000,000.0
2026 Notes | Secured Debt
Restructuring Cost and Reserve [Line Items]
Face amount	2,000,000,000.0			2,000,000,000.0		2,000,000,000.0
2029 Notes | Secured Debt
Restructuring Cost and Reserve [Line Items]
Face amount	2,000,000,000.0			2,000,000,000.0		2,000,000,000.0
Term Loan Facility | Secured Debt
Restructuring Cost and Reserve [Line Items]
Face amount	1,400,000,000			1,400,000,000		1,400,000,000
Credit Agreement | Secured Debt | Revolving Credit Facility
Restructuring Cost and Reserve [Line Items]
Face amount	1,000,000,000.0			1,000,000,000.0		1,000,000,000.0
CARES Act Term Loan Facility | Secured Debt
Restructuring Cost and Reserve [Line Items]
Face amount	520,000,000			520,000,000		$ 520,000,000
Azul
Restructuring Cost and Reserve [Line Items]
Nonoperating unrealized gains	57,000,000			35,000,000
Gain (loss) on equity securities					284,000,000
Clear Secure, Inc.
Restructuring Cost and Reserve [Line Items]
Nonoperating unrealized gains	$ 90,000,000			$ 90,000,000
BRW | Term Loan Receivable
Restructuring Cost and Reserve [Line Items]
Nonoperating credit loss on BRW Term Loan and related guarantee					697,000,000
Routes
Restructuring Cost and Reserve [Line Items]
Impairment of intangible assets			$ 80,000,000		$ 130,000,000
Employee Separation | Voluntary Separation Leave Programs
Restructuring Cost and Reserve [Line Items]
Number of employees electing to voluntarily separate from the company | employee		4,500		4,500
Special termination benefits related to VSL programs		$ 46,000,000		$ 46,000,000
Employee Separation | Voluntary Separation Leave Programs | Full-Time Employees
Restructuring Cost and Reserve [Line Items]
One-time per employee contribution for special termination benefits related to VSL programs		125,000
Employee Separation | Voluntary Separation Leave Programs | Part-Time Employees
Restructuring Cost and Reserve [Line Items]
One-time per employee contribution for special termination benefits related to VSL programs		$ 75,000