In a blunt letter to transport chiefs, British Airways (ICAG.L), bmi (LHAG.DE), Virgin Atlantic and Easyjet (EZJ.L) said time was running out to tackle the expected surge in air traffic and its impact.

Failure to address their concerns could bring misery to millions of regular travellers and those coming to London for the world's biggest sporting event, the airlines argue.

"As the situation currently stands the industry believes that there is a significant risk of severe delay and disruption at all of London's major airports unless urgent action is taken," they wrote in a letter seen by Reuters on Saturday.

"Time is running out to ensure that any changes to procedures and the appropriate training are in place prior to the Games."

Britain, already the sixth most visited country in the world, anticipates an additional 700,000 international travellers during the Olympics, which begin on July 27.

London's Heathrow Airport, Britain's busiest, runs at 99 percent of its capacity on an average day, and Gatwick, south of the capital, is operating at full capacity at peak times, while unforeseen events such as poor weather conditions have caused huge problems and queues in the past.

Businesses and airlines have long argued that Heathrow needs a third runway to cope with rising demand, a move blocked by the government because of environmental concerns.

On Thursday, Willy Walsh, chief executive of International Airlines Group IAG.L, which owns BA and Spain's Iberia, described Britain's aviation policy as an "unholy mess".

In the letter to the government, whose signatories included Andy Lord, director of operations at BA, and Corneel Koster, Virgin's director of operations, safety and security, the airlines highlighted six areas of concern.

AIR SPACE FEARS

These include the resilience of air space in coping with the number of planes taking off and landing during the Olympics, the impact of any adverse weather, and the effect any security incident might have.

It said air traffic controllers had put forward five proposals about prioritising flights in southeast England during the Games but these had been rejected by the Civil Aviation Authority CAA.L.

Meanwhile the government's Department for Transport (DfT) was wrongly under the impression that the industry was happy with the steps that had been taken so far, they wrote.

"This is far from the truth," said the letter, also signed by Easyjet's Chief Operations Officer Warwick Brady and Sean Butler, head of operations at bmi.

A meeting between the airlines, the DfT and CAA is planned for March 22 and the letter said it was vital that a deal was reached then. "Failure to respond leaves the UK vulnerable to the type of major disruption that will cause significant reputational damage and would be foolhardy and reckless."

A DfT spokeswoman said it had already promised a range of special measures to prevent scheduled air services from disruption, by increasing air space capacity as well as putting in temporary restrictions for some air traffic.

"We are confident that the majority of these additional issues have now been addressed and we look forward to discussing them with the airlines concerned at a meeting next week," the spokeswoman said.

(Editing by Mark Heinrich)

• A Permanent Economic Emergency