Thousands of air passengers are expected to face another day of disruption today.
Chaos ensued yesterday at airports across the country following the introduction of new anti-terror measures as the authorities reported that a major terrorist plot to blow up US-bound aircraft had been thwarted.
Some operators were insisting that flights schedules would return to normal today, but some flights have been cancelled and lengthy delays are expected.
Yvonne Kraska, a customer service agent for Lufthansa based at its call centre in Melbourne, Australia, said of UK flights: "Our flights are trying to leave on schedule or as close to the schedule as possible.
"We tell our passengers to arrive early and not to bring any liquid items with them.
"We have given one day's grace for people if they don't wish to travel today and are allowing them to re-book their flights to later flights.
"But we have not had any information that the flights aren't leaving at all or that we have to rebook everyone."
On a statement on its website, British Airways said it expected to operate the "vast majority" of its flights today, but advised customers to check ba.com for the latest flight information before leaving home and to allow plenty of time for their journey.
The statement said: "The airline anticipates that it will operate all long-haul flights from London Gatwick and all long-haul flights from London Heathrow with the exception of some flights to the US.
"The entire short-haul flying programme from London Gatwick is expected to operate as normal with the exception of all nine domestic flights due to depart before midday which have been cancelled.
"Around 60% of short-haul and domestic services to and from London Heathrow are expected to operate."
It added: "All short-haul and domestic services operated by regional subsidiary BA Connect to and from UK regional airports (not Heathrow and Gatwick) should operate as normal, albeit with some delays."
But the statement added that "operational disruption is expected to continue".
It said that the airline had decided that no hand baggage would be allowed in the cabin on inbound British Airways' flights to the UK from the USA to speed up the departure process from the USA.
A statement on Aer Lingus's website said that as of 3pm yesterday "all Aer Lingus flights are operating on schedule to/from all UK airports".
"Passengers intending to travel should note that they may experience some delays, but they should check-in as normal," it said.
Heathrow airport operator BAA said on its website: "Due to the heightened security at UK airports, Heathrow is experiencing significant disruption to its operations.
"The airport is open and hopes to return to near normal operations, within the new restrictions, in the next few days.
"The additional security restrictions will continue to have an impact on the airport's operation.
"However we are working hard, in conjunction with our airlines and control authorities, to deliver as normal a service as possible.
"Some flights will inevitably be cancelled. Therefore anyone who intends to travel in the next few days should check with their airline."
According to a Sky News report, the situation at Stansted airport at 4.40am today was still "very chaotic".
"Airlines are assuring us the flights are, and will be, setting off but there are still am amazing amount of people here. It is not even 5am. People are sleeping on the floor," Sky reported.
Yesterday thousands of passengers experienced travel chaos with many flights cancelled and Heathrow closed to incoming short-haul services.
British Airways cancelled all short-haul flights in and out of Heathrow until 3pm yesterday and by late morning had had to axe more than 200 of the 550 flights it normally operated out of the west London airport daily.
Low-cost carrier Ryanair was another of the airlines badly hit - cancelling nearly 100 flights.
Many foreign airlines suspended services to London even before Heathrow airport operator BAA announced a suspension of short-haul Heathrow-bound flights that had not already left for London.
Those axing flights to London included Italian carrier Alitalia, German airline Lufthansa, Spanish carrier Iberia and Irish airline Aer Lingus.
Air France scrapped five of its Heathrow to Paris flights.