Commitments and Contingencies - Firm Commitments and Options to Purchase Aircraft (Details)	Jun. 30, 2021 commitment	Jun. 27, 2021 aircraft
Airbus A321XLR
Long-term Purchase Commitment [Line Items]
Number of firm commitments	50
Scheduled Aircraft Deliveries
Last Six Months of 2021	0
2022	0
2023	0
After 2022	50
Airbus A321neo
Long-term Purchase Commitment [Line Items]
Number of firm commitments	70	70
Scheduled Aircraft Deliveries
Last Six Months of 2021	0
2022	0
2023	16
After 2022	54
Airbus A350
Long-term Purchase Commitment [Line Items]
Number of firm commitments	45
Scheduled Aircraft Deliveries
Last Six Months of 2021	0
2022	0
2023	0
After 2022	45
Boeing 737 MAX
Long-term Purchase Commitment [Line Items]
Number of firm commitments	380
Scheduled Aircraft Deliveries
Last Six Months of 2021	13
2022	40
2023	122
After 2022	205
Boeing 787
Long-term Purchase Commitment [Line Items]
Number of firm commitments	8
Scheduled Aircraft Deliveries
Last Six Months of 2021	8
2022	0
2023	0
After 2022	0