Heathrow has warned its £33bn third runway project could spiral into a budget disaster like the HS2 high-speed rail scheme unless it implements stronger cost controls. The airport proposes creating a new oversight panel with veto power for airlines and technical experts to monitor spending, aiming to avoid the £100bn-plus overrun seen in HS2. £30bn is the threshold where airline economics break, according to a report commissioned by British Airways owner IAG, which fears landing fees could surge. Heathrow argues UK costs are higher than European or Middle Eastern airports, but airlines demand regulatory reform including competition to keep expansion affordable and on budget.

The CAA will soon rule on the project's viability, with Heathrow investors awaiting a final investment decision.