Airline passengers will have to put up with more rigorous security checks for a long time to come. Officials at the Department for Transport have made it clear that the terrorist threat, though no longer critical, is still “real, here, deadly and enduring”. There may be some small relaxation of the intrusive inspections, and allowable hand baggage dimensions will soon revert to the international standard. But the restrictions on liquids and on other items that can be taken on board are likely to remain in force.

This has long-term consequences. First, it is clear that BAA, which operates Heathrow, Gatwick and Stansted, as well as the increasingly busy regional airports, must make proper provision to cut back the long queues and waiting times. That means hiring more staff. BAA is seeking up to 1,000 additional personnel to conduct the extra searches as well as enforcing the more stringent regulations. Secondly, the airports will have to make more space available for security — sacrificing retail space if necessary. Even before the discovery of the terror plot, huge queues regularly clogged the area near the body scanners, forcing passengers to wait half an hour or more. The airport authorities not only need to install more scanners and more sophisticated electronic sniffers, but to make room available for those waiting. Thirdly, there has to be a permanent, long-term watch on the activities of all those employed in the industry and especially in the airside shops: terrorist organisations, if thwarted in attempts to board aircraft, will look at other ways to compromise security.

All this will cost money. Inevitably, the airport authorities will pass on the costs to the carriers, which have no choice but to increase fares. Passengers must expect to pay more to travel. The days of peppercorn fares are over. The airlines themselves will also have to employ more staff. It is unrealistic to imagine that proper security can be enforced in the air with only a skeleton cabin crew.

Airports, however, can do only so much. The terrorist threat, as security officials admitted yesterday, cannot be uninvented, even if more sophisticated machinery can detect liquid explosives. To rely entirely on scanners and searches would be wrong: intelligence must be the main defence against terrorism. That means that more should be done to monitor suspicious behaviour and concentrate on passenger risk.

This is politically sensitive. The panicky reaction of passengers on some flights and unacceptable ejection of those with beards, speaking Arabic or looking like a stereotypical Islamist extremist have shown how the risk of crude profiling comes close to constituting the new offence of “travelling while being Asian”. El Al, the Israeli airline, however, has been successfully using passenger profiling to enforce security for years. Grandmothers or schoolchildren can usually be checked through quickly. Britain cannot enforce measures in isolation: long-term security must be uniform across Europe. But no one should imagine that it will soon become less intrusive. Nor should it.