COMMITMENTS AND CONTINGENCIES - Aircraft-Related Commitments (Details)	Sep. 30, 2026 aircraft
Firm Orders
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	180
Options and Other Rights
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	71
B737 | Firm Orders
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	168
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