'Travellers face years of air security alerts'

Mr Darling refused to discuss press reports that the Government had received intelligence that fundamentalist terror network al-Qaida was planning to use BA flights to launch suicide attacks on prominent targets in the USA.

But he insisted the decision to cancel the flights, as well as one to the Saudi Arabian capital Riyadh, were “justified” on the basis of intelligence warnings.

Cancellations would remain a rare exception, occurring only in “extreme cases”, predicted Mr Darling, who said the Government was determined to balance the need for additional security with the aim of allowing people to travel as freely as possible.

He told BBC1’s Breakfast with Frost: “What I can say is that I fear that for many years to come, we are going to be living in an age where there is going to be a heightened state of alert. Sometimes it will be quite severe, at other times perhaps less so.

“We are going to have to get used to increased security at airports. From time to time that will be noticeable and at other times maybe things will be going on behind the scenes.”

Mr Darling added “A decision to cancel a flight is comparatively rare. But where we have to cancel a flight, the grounds are very clear in our minds and we are justified in taking that decision.”

Information was coming in to governments around the world every day, and was evaluated by intelligence experts before being discussed by ministers, said Mr Darling.

He would not reveal the nature of the intelligence because “in doing so, we would be telling the very people we are concerned about what it is that the Government does or doesn’t know”.

The final decision on this week’s cancellations was taken by BA.

“The airline, at the end of the day, attaching a very, very high premium on safety, acting on our advice, decided on the information it had it would be better to cancel those two flights,” said Mr Darling.

“But the flight went yesterday and I hope they will be able to continue to fly that particular route without further interruption.”

The Transport Secretary acknowledged that intelligence on potential threats was sketchy, by its very nature, and that some of the information gathered was bound to be inaccurate.

“It is about putting bits together and trying to build a picture,” he said. “At the end of the day, we have got to reach a judgement based on the information we have as to whether, in extreme cases, a flight has to be cancelled or whether other measures would be adequate.”

Where possible, the authorities would act to neutralise threats to flights, said Mr Darling. But in some cases, the nature of the threat made it impossible to be certain that a particular flight was safe to take off.

“The first line of defence, and the best possible thing you can do is to stop somebody or stop something that you are concerned about getting onto an aeroplane,” he said.

“However, there will be cases – and they are comparatively rare – where it may be necessary to go further and to ground a particular flight. It really depends on the information that we have got.”