A report by the Competition Commission which could signal a break-up of the British Airports Authority has been welcomed by three leading airlines.
EasyJet, bmi and Ryanair all endorsed the initial recommendations made by the commission, which suggested it might not be in the interest of airlines or passengers for BAA to continue owning seven airports.
BAA, which is owned by Spanish firm Ferrovial, owns Heathrow, Gatwick, Stansted, Southampton, Edinburgh, Glasgow and Aberdeen airports.
Andy Harrison, easyJet chief executive, said: "Breaking up BAA alone is not enough or even the first step. We need a fundamental overhaul of UK airport regulation which will introduce more competition and tougher regulation. Transferring ownership of our major airports from one highly indebted monopolist to another will benefit no one apart from the City deal-makers."
Nigel Turner, bmi chief executive officer, said: "We identified last year that BAA's high market share for air passengers appears to prevent, restrict or distort airport competition within the UK. We strongly believe that to ensure future real intra-airport competition in the UK, the only option facing the regulators is the dismantling of BAA's monopolistic grip over the UK's busiest airports in the south-east and Scotland."
A Ryanair spokesman said that if Stansted was ultimately sold, current multi-billion pound development plans could be shelved since "none of the users want them anyway".
He added: "This report is a substantial victory for Ryanair in that this is really as far as we expected the commission to go at this stage."
Ryanair has campaigned vigorously for the break-up of BAA's near-monopoly of London airports, claiming the situation greatly disadvantages both passengers and airlines.
In a recent flare-up, the low-cost carrier announced it was withholding the latest landing charges increase at Stansted in protest at a levy to fund Stansted's development plan.