Airport RAB Regulation Explained
Aena DORA II RAB €9,387.1m, IMAAJ €10.35/passenger and 7.68% WACC; Heathrow H7 3.16% RPI-real; Auckland Part 4 disclosure versus classic RAB regulation.
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.
RAB Airports Earn on an Approved Base, Not Pure Volume × Price
On a demand-risk toll road, revenue is trips times tariff and the operator eats traffic shortfalls. On a RAB-regulated airport, the regulator sets (or approves) an asset base and an allowed return; aeronautical charges recover that return plus depreciation and efficient costs. Passenger growth still moves retail and some international assets, but the core tariff comes from a regulatory formula rather than a market-clearing toll price.
That split is why traffic-GDP linkage defaults differ between motorways (~1.0× GDP) and developed airports (~1.3× income) on demand-exposed lines, while Spanish aeronautical revenue ties to DORA mechanics.
Aena: DORA II in Numbers
Aena operates Spain’s regulated airport network under DORA II, the regulatory framework covering 2022-2026. There is no single concession expiry on the Spanish system, so analysts track regulatory-cycle remaining instead of IFRIC 12 reversion on the core network.
| DORA II metric | Value | As-of |
|---|---|---|
| Average RAB | €9,387.1m | End-2024 |
| WACC on RAB (pre-tax) | 7.68% | DORA 2022-2026 |
| Regulated charge (IMAAJ) | €10.35/passenger | 2025; 0% change vs 2024 |
| FY2025 passengers | +4.2% to 384.8M | FY ended 31 Dec 2025 |
| FY2025 EBITDA margin | 59.3% | Same period |
| Net debt / EBITDA | 1.46× | 31 Dec 2025 |
Mini-example (regulatory return on RAB, illustrative): Apply the filed 7.68% pre-tax WACC to average RAB €9,387.1m:
€9,387.1m × 7.68% ≈ €721m pre-tax return on the approved base before other DORA charge components.
That arithmetic is a first pass, well short of CNMC’s full charge stack. RAB and WACC are the starting inputs on Aena; an EV/EBITDA multiple is a cross-check that comes later.
DORA III, covering 2027-2031, is now set. Aena proposed 9% WACC and CNMC recommended 7.4% in June 2026; the Council of Ministers approved 8.32% pre-tax on 15 September 2026 (BOE, 19 September 2026). A model that runs into 2027 uses 8.32% from that year.
Heathrow H7: UK RAB Context
The UK CAA’s final decision after the CMA appeal (July 2024) set Heathrow’s H7 vanilla WACC at 3.16% RPI-real, down from 3.18% in the March 2023 final decision, with 60% notional gearing. Heathrow is the reference point for RPI-real, UK-style airport price control in investor materials even when the comp set name is Aena or Auckland Airport.
| Aena DORA II | Heathrow H7 (CAA) | |
|---|---|---|
| Base | Average RAB €9,387.1m | RAB-style regulatory capital |
| Allowed return metric | 7.68% pre-tax WACC × RAB | 3.16% RPI-real vanilla WACC (Jul 2024) |
| Cycle | 2022-2026 | H7 control period |
| Passenger charge marker | €10.35 IMAAJ | Set in CAA charge control |
Do not subtract 3.16 from 7.68 and call it a spread. Real versus nominal, tax gross-up, and gearing definitions differ.
Auckland Runs Information-Disclosure Regulation, a Different Regime From Aena’s RAB
Auckland Airport is regulated under a different structure to Aena’s published RAB build:
| Feature | Auckland (AIA) | Aena Spanish network |
|---|---|---|
| Framework | Commerce Act Part 4 information disclosure | DORA statutory RAB |
| Asset life | Land vested under 1988 Order; no lapse date | No single expiry; regulatory periods |
| Pricing period | PSE4 to 30 June 2027 | DORA II to 2026 |
| Return target | Commission review cut charges targeting 7.82% return (post-Mar 2025) | 7.68% WACC × RAB |
| FY2025 EBITDA margin | ~69.8% (EBITDAFI derived) | 59.3% |
| Leverage | ~2.32× net debt/EBITDA; gearing 12.8% | 1.46× net debt/EBITDA |
Analysts still model charges, returns, and capex, but they cannot lift Aena’s RAB table and drop it onto Auckland. Label Auckland information-disclosure regulation when comparing frameworks.
Vinci Airports: Regulated Fees Plus Demand
Vinci Airports (63.4% segment EBITDA margin FY2025; passengers +5.0% to 334M) mixes regulated fees with demand exposure across a portfolio of airport concessions (Lyon to 2047, ~22 years remaining per 2023 URD). International PPP assets behave like finite-life concessions; French and other regulated fee structures behave like partial RAB or tariff-cap regimes depending on the airport.
Use the RAB lens for Aena core Spain and UK H7 references; for Luton (~6.7 years to September 2032) and other expiring PPP stakes, model contractual expiry separately from DORA charge mechanics.
Linking RAB to Valuation
RAB-regulated cash flows sit in a ~10-14× EV/EBITDA range, the working benchmark for regulated or availability-style concessions, below demand-risk toll roads’ ~12-16× range. Where contracts expire, run a finite-life DCF to that date. On Aena Spain, the horizon is the regulatory cycle: DORA II ends 2026 and DORA III runs 2027-2031 at 8.32% pre-tax.
Tariff escalation on regulated motorways (≥70% of CPI on French networks) sits in the escalators guide. Airport aeronautical charges move through regulatory resets instead, a different mechanism from deed-level CPI floors.
Transport Infrastructure Sector Primer
Concession life, traffic growth and the toll escalator feed a finite-life DCF with no terminal value, landing a concession value to weigh against the EV/EBITDA shortcut.
The Excel model is the primer's concession build live across 9 sheets: a finite-life after-tax free-cash-flow DCF with zero terminal value, a WACC build block (risk-free rate, equity risk premium, relevered beta and cost of debt), a traffic-and-tariff build, a regulated-versus-demand-risk two-mode switch, a leverage screen and a multiples cross-check. Change the remaining life, any WACC input or the traffic growth and the concession value moves; the cross-check and leverage sheets update alongside it.
Frequently Asked Questions
- What is an airport Regulated Asset Base (RAB)?
- The RAB is the regulator-approved asset base on which an airport operator earns an allowed return, typically WACC × RAB plus depreciation and operating cost recovery. Aena's Spanish network uses DORA II with average RAB €9,387.1m (end-2024) and a pre-tax WACC of 7.68% on that base. It is not the same as enterprise value or IFRS property, plant and equipment.
- How does Aena charge passengers under DORA II?
- The regulated charge IMAAJ for 2025 is €10.35 per passenger, unchanged from 2024. DORA II runs 2022-2026. Revenue quality comes from the regulatory formula on RAB and allowed return, not pure volume × market price on the core Spanish network.
- What is Heathrow H7 WACC and how does it compare to Aena?
- The UK CAA's final decision after the CMA appeal (July 2024) set Heathrow's H7 vanilla WACC at 3.16% RPI-real, with 60% notional gearing. Aena DORA II WACC is 7.68% pre-tax on average RAB. The levels are not directly comparable without converting real/nominal bases, tax treatment, and gearing assumptions.
- Is Auckland Airport regulated like Aena?
- No. Auckland operates under Commerce Act Part 4 information disclosure, not a classic RAB build-up like Aena or UK CAA price control. Its current pricing period, PSE4, runs to 30 June 2027; the Commerce Commission's March 2025 review targeted a 7.82% return for the final PSE4 years. Land is vested under the 1988 Order with no lapse date.