UK airport authority BAA has warned that air passengers are likely to face further delays today, despite the relaxation of security restrictions on hand luggage.
An outright ban on hand luggage, implemented in the wake of last week's alleged terror plot to blow up transatlantic airliners, was lifted at London's Heathrow and Gatwick airports this morning, a day later than most other airports around the UK.
The government's decision to ease hand luggage restrictions was announced yesterday after the Home Office downgraded the terror threat level facing the UK from "critical" to "severe".
In response, BAA warned that it would not be able to implement the changes at Heathrow and Gatwick airports until this morning.
But despite the revised regulations, which will now allow passengers to carry one item of cabin baggage on to flights, BAA stressed that the easing of restrictions did not represent a "return to normal" at Britain's airports.
Under the new rules, hand luggage carried by passengers must be no bigger in size than a small laptop bag or rucksack. Liquids will still be prohibited and toiletries, cosmetics and sharp objects are also banned from hand baggage.
In a statement this morning, BAA warned: "The revised regulations will continue to have an impact on our airport operations. Passengers are asked to be patient while these additional security measures are in place.
"Delays are likely, and anyone travelling over the next few days is asked to allow extra time for their journey and to arrive at the airport prepared," the statement added.
As a result of the continuing security restrictions, 45 flights have been cancelled from Heathrow today. British Airways (BA) has cancelled 21 shorthaul flights, four longhaul services and 16 domestic services from the airport, while a scheduled Jet Airways flight has also been pulled.
At Gatwick, BA has cancelled 11 domestic flights, while Ryanair has cancelled eight of its departures from London's Stansted.
Both airlines have criticised BAA for not being better prepared for the increased security measures, with BA chief executive Willie Walsh last night warning that his company may sue the airports operator for compensation after being forced to cancel large numbers of flights.
"Since 9/11, everyone in the industry has known there might be times when extra security measures needed to be put in place," Mr Walsh told the Daily Mirror.
"Yet when the moment struck, BAA had no plan ready to keep Heathrow functioning properly."
"The queues for security have wound all round the terminals like a bad dream at Disneyland," he added.
But BAA chief executive Tony Douglas insisted that the airline industry had faced a "national security challenge" on an "unprecedented scale" over recent days.
Meanwhile, one of Britain's most senior Muslim police officers has criticised reported government plans to introduce a system of "passenger profiling" at the country's airports to help airlines identify those they believe could pose a risk to security.
The Times reports that Department of Transport officials are considering the system which would use intelligence to examine factors such as passengers' travel histories.
But Mr Desai told the BBC2's Newsnight that such a system would be "hugely problematic" if it targeted people from certain ethnic backgrounds.
"What you are suggesting is that we should have a new offence in this country called 'travelling while Asian', he said.
"That's unpalatable to everyone. It is communities that defeat terrorism, and what we don't want to do is actually alienate the very communities who are going to help us catch terrorists," Mr Desai added.