COMMITMENTS AND CONTINGENCIES - Aircraft-Related Commitments (Details)	Mar. 31, 2026 aircraft
Firm Orders
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	189
Options and Other Rights
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	71
B737 | Firm Orders
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	174
B737 | Options and Other Rights
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	71
B787 | Firm Orders
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	12
B787 | Options and Other Rights
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	0
E175 | Firm Orders
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	3
E175 | Options and Other Rights
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	0