The airline industry faces losing millions of pounds in lost revenue following the discovery of the terror plot yesterday.

The average cost for each plane on the Heathrow to New York route that was grounded following the police raids is estimated to between £350,00 to £400,000.

With more than 500 flights cancelled yesterday, operators could face missing out on up to £200 million in revenue.

Although the airlines would be spared fuel, landing and tax costs from not taking off, they would also have to pay salaries of their crews.

British Airways shares fell five per cent, wiping around £200 million off the value off the company, while low-cost rivals Ryanair and easyJet were down two per cent.

And retailer WHSmith lost one per cent as analysts noted the prevalence of stores at UK airports. The shops normally benefit from the feel-good factor when people go on holiday and stock up on books and newspapers, but passengers have been banned from carrying anything other than essential items on planes.

Dr Pat Hanlon, an aviation expert at Birmingham Business School, said: "Although there will be no question of compensation, because this is an act of terrorism, companies will lose a lot of revenue because they will have to refund the passengers on the cancelled flights.

"On top of that there will be dislocation costs caused by planes being out of position. This means that some flights will have to take off with less than full capacities to get back to their normal schedules."

Dr Hanlon said the discovery of the plot could also have long term implications for the industry and could ultimately trigger a new round of mergers.

"After every event like this people are put off flying. This is potentially worse than 9/11 because people wonder what might have happened."

The aviation industry was picking up after a disastrous time in the wake of the September 11 attacks, which forced many of the main American airlines to file for bankruptcy.

"Passenger numbers after September 11 went down sharply, but the cycle has recovered and this year has been particularly good for trans-Atlantic travel. There have been more Americans vacationing in Europe than at any time since 9/11.

"But this news will have had a big impact in America and will be a big set back."

Meanwhile, accountants Grant Thornton estimated the chaos that hit the UK airports could cost the British economy £10 million a day.