COMMITMENTS AND CONTINGENCIES - Aircraft-Related Commitments (Details)	Mar. 31, 2025 aircraft
Firm Orders
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	84
Options and Other Rights
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	100
B737 | Firm Orders
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	70
B737 | Options and Other Rights
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	100
B787-9 | Firm Orders
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	9
B787-9 | Options and Other Rights
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	0
E175 | Firm Orders
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	5
E175 | Options and Other Rights
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	0