Airline Free Cash Flow and the Capex Cycle
Non-GAAP vs computed FCF for DAL, UAL, AAL and LUV; FY2025 FCF compared; capex cycle and deleveraging targets; why the label on FCF matters as much as the sign.
Educational analysis for professional use. This guide is not investment advice or a recommendation to buy or sell any security, and it is not personalised.
FCF Is the Post-COVID Equity Story, If You Read the Footnote
Since 2022 the airline equity case has often been that free cash flow pays down pandemic debt. That case is only as good as the FCF line behind it, and for FY2025 the four large US carriers used four definitions: non-GAAP reconciliations at Delta and United, a company definition at American, and none at all at Southwest. Check what each figure leaves out, and whether capex is normal or at a fleet-replacement peak.
The FCF Definition Zoo
International Airlines Group (IAG, owner of British Airways and Iberia) reports an APM, an alternative performance measure: the European equivalent of non-GAAP.
| Carrier | FY2025 FCF | Definition | Source line |
|---|---|---|---|
| Delta | $4.64B ($4,643M) | Non-GAAP FCF reconciliation | 8-K EX-99.1 |
| United | $2.71B ($2,710M) | Non-GAAP FCF reconciliation | 8-K EX-99.1 |
| American | −$83M | Company-defined FCF | Earnings presentation |
| Southwest | −$831M | Computed: OCF $1,842M − capex $2,673M | Cash flow statement |
| IAG | €3,146m | APM: OCF €6,588m − capex €3,442m | FY2025 results release |
| Ryanair | €1,863m (computed; year to 31 Mar 2025) | OCF €3,415.7m − capex €1,552.5m | Cash flow statement |
Delta, United and American start from operating cash flow plus net investing cash flow, so aircraft sale proceeds reduce capex, then strip out short-term investment movements and a few footnoted items. Operating cash flow minus capex is cruder but comparable where no reconciliation exists.
Under IFRS 16, the international lease standard, IAG and Ryanair book lease principal repayments in financing cash flow, outside FCF: IAG repaid €1,344m of lease liabilities in 2025. US carriers pay lease rent inside operating cash flow, so their FCF already bears that cost and IAG’s does not. Any non-GAAP figure can also leave out pension contributions or maintenance capex booked elsewhere; the footnote says which.
FCF Against Net Debt
FCF divided by net debt is the share of debt one year’s cash would retire if all of it went to repayment.
| Carrier | FY2025 FCF | Net debt (incl. leases) | FCF / debt |
|---|---|---|---|
| Delta | +$4.64B | $14.3B adj. | ~32% |
| United | +$2.71B | $19.9B adj. | ~14% |
| American | −$83M | $30.7B (also includes pension) | Negative; total debt $36.5B, guided below $35B in 2026 |
| Southwest | −$831M | ~$2.75B adj. (adjusted debt less cash) | Negative |
Delta and United also file leverage targets on EBITDAR, which is EBITDA before aircraft rent (EBITDAR leverage guide): about 2× gross for 2026 at Delta, <2.0× net at United. American, with the most net debt of the three network carriers, has no ratio target.
The Capex Cycle
Airline capex comes in waves of new narrowbodies, cabin retrofits, engines, IT and airport projects, and a carrier’s place in that cycle drives much of its FCF. Southwest generated cash from operations in FY2025 yet showed negative FCF because it was in a fleet-investment year, the same year it stopped hedging and bought fuel at market prices. That need not be permanent, but the equity case needs FCF to recover once capex settles.
Positive FCF is not spare cash either. Until leverage is back near the ~2× EBITDAR targets, it goes to debt before buybacks.
Worked Mini-Example: FCF at Mid-Cycle Fuel
Take an illustrative carrier flying 200bn available seat miles (ASMs, one seat flown one mile). Total revenue per ASM (TRASM) is 18.0¢. Cost per ASM excluding fuel (CASM-ex) is 13.0¢, which still includes depreciation and aircraft rent. It burns 15 gal/1,000 ASMs at a mid-cycle $2.85/gal. D&A is $2.0B, aircraft rent $1.55B and simplified maintenance capex $3.0B/yr.
| Line | Amount |
|---|---|
| Operating income: revenue $36.0B less non-fuel costs $26.0B and fuel $8.55B | ~$1.45B |
| Add back non-cash D&A | $2.0B |
| EBITDA (rent still deducted) | ~$3.45B |
| Less capex | −$3.0B |
| Simplified FCF, before interest, tax and working capital | ~$0.45B |
Rent stays in because it is paid in cash. Adding it back gives EBITDAR of about $5.0B, the figure leverage is measured on, though the rent still has to be paid.
Raise fuel to $3.35/gal (+$0.50): operating income falls ~$1.5B and FCF turns negative.
At 2.0× EBITDAR leverage on that $5.0B, adjusted net debt is $10.0B, and ~$0.45B of FCF before interest and tax would retire at most ~4.5% of it a year. Delta’s FY2025 ratio was ~32%.
Screening Checklist
- Which FCF line? A non-GAAP reconciliation, a company definition, or operating cash flow minus capex.
- Capex phase: replacement or growth, and does operating cash flow cover capex at mid-cycle fuel?
- The ex-fuel spread, unit revenue less unit cost excluding fuel, sets the ceiling on sustainable FCF (see the RASM and CASM guide).
- Leverage target: a filed ratio, or only debt-dollar guidance?
EBITDAR builds from a thin unit margin on seat miles, the leases are capitalised into net debt, and the value moves on what a small load-factor drop costs.
The Excel model is the primer's airline build live across 11 sheets: EBITDAR from seat miles and unit margin, leases capitalised into adjusted net debt, a through-cycle EV/EBITDAR valuation for a network carrier and a low-cost carrier, a load-factor downturn, a lease-adjusted leverage screen and a sensitivity grid. Change the unit revenue, fuel or leases and the value moves.
Frequently Asked Questions
- How do airlines define free cash flow?
- There is no single definition. Delta and United publish non-GAAP FCF reconciliations (FY2025: Delta $4.64B, United $2.71B). American reports company-defined FCF (−$83M FY2025). Southwest publishes no FCF line; operating cash flow of $1,842M minus capex of $2,673M gives −$831M. Always read the reconciliation footnote.
- Why did Southwest report negative free cash flow in FY2025?
- Capex of $2,673M exceeded operating cash flow of $1,842M, leaving −$831M. Heavy fleet and infrastructure spending on a ~3.2¢ gap between unit revenue and unit cost excluding fuel, with 77.4% of seats filled, left less cash for debt repayment than at Delta or United.
- Can an airline be FCF-positive and still delever slowly?
- Yes, if capex, lease payments, pensions or working capital absorb cash outside the headline FCF line, or if the starting net debt is large. American reported −$83M company-defined FCF against $30.7B net debt in FY2025. Delta's $4.64B non-GAAP FCF against $14.3B adjusted net debt supports faster paydown toward its guidance of about 2× gross leverage for 2026.
- How does fuel affect airline free cash flow?
- Fuel hits operating cash flow before capex. For an illustrative carrier flying 200bn available seat miles, a +$0.50/gal move from a $2.85/gal mid-cycle price costs roughly $1.5B of operating income, which flows through to FCF unless working capital or hedging shifts the timing. Unhedged carriers such as Southwest take that swing directly.