If passengers endure long security queues and disgusting toilets at Manchester airport, they can choose to fly next time from its arch-rival in Liverpool.

In the Midlands, passengers have Birmingham and Nottingham airports competing fiercely for their business by keeping costs low and service quality high.

But for the large majority of passengers in central Scotland, the only alternative to one BAA airport is another BAA airport. In the South East of England with Heathrow, Gatwick and Stansted, the Spanish-owned company controls more than 90 per cent of the market. Luton and London City can only nibble at the edges.

When people queued for more than an hour last summer to go through Heathrow's metal detectors, there were no advertisements from Gatwick or Stansted saying: “Come to us for a better service”.

That could change by 2010, if the Competition Commission follows through on the strong hints in the report that it is considering breaking up BAA's monopoly.

The company has argued for the past decade that common ownership of the big three South East airports is essential to delivering extra capacity. Heathrow and Gatwick are already almost full and Stansted is two thirds full. BAA says that only it has the expertise and the financial muscle to deliver new runways and terminals.

The Government has preferred to do business with a monopoly owner which has always been willing to allow the Department for Transport to dictate the agenda. BAA made no demands and simply waited for the Government to announce that it wanted the first new runway at Stansted and the second at Heathrow.

But it is this willingness to cooperate that is likely to bring about BAA's downfall. The commission yesterday demolished BAA's central argument against expansion simply by reversing it. It said that the monopoly, far from being the key to expansion, was the main reason why expansion was proceeding so slowly, leaving passengers in overcrowded terminals and circling in aircraft stacks. The commission suggested that, under separate ownership, London's main airports would compete for the right to expand and extra runway capacity would be delivered more quickly.

A new owner of Gatwick would ignore the gentleman's agreement between the Government and BAA to talk down expansion and immediately start planning a new runway and terminal.

However, the simple idea that competition would deliver the best solution presupposes that the market will be allowed to expand to meet demand. But environmental arguments against expansion have become so loud that no new runway will be built unless the Government fights tooth and claw for it.

All hope of delivering significant new capacity could be lost if rival companies start arguing over whose airport should be allowed to grow.

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