A third of flights due to leave the world's busiest airport today have been cancelled despite a plea by the airlines for measures to alleviate the problems caused by new anti-terror measures.
The move follows a row between the airport's operator, British Airports Authority (BAA), and airlines over who is to blame for the continuing delays and cancellations in the wake of the chaos caused by Thursday's bomb plot security alert.
BA chief executive Willie Walsh accused BAA of being unable to deal with increased security and baggage checks and Ryanair ceo Michael O'Leary claimed the passenger disruption was "solely" due to this.
But BAA's chief executive officer for Heathrow, Tony Douglas, blamed the measures themselves, saying they were "not sustainable".
Other airlines had some sympathy for BAA. Paul Charles, director of communications at Virgin Atlantic, said it was "supportive of BAA because they are having to do a very difficult job in extreme circumstances".
Likewise, low-cost airline easyJet praised BAA, saying its services were back to business with no "unusual delays" or cancellations yesterday.
Meanwhile, budget airline Ryanair called for urgent government action to reduce the passenger backlog at London's airports or risk them grinding to a halt.
The airline's chief executive said Heathrow, Gatwick and Stansted could not cope with the new security measures which require all passengers to undergo a body search and called on the Government to provide extra staff to help ease the pressure.
BAA said up to a third of all flights due to leave Heathrow today had been cancelled.
The airline operator said the remaining flights were expected to depart from the airport on time or with as little delay as possible.
In a statement it said: "BAA sincerely regrets this disruption and thanks passengers for their patience. Passengers are urged to check with their airlines before travelling to the airport."
A BA spokeswoman said it had cancelled 30 per cent of its flights in and out of Heathrow today.
She added that all 23 domestic flights to and from Gatwick today had been cancelled, excluding flights to Jersey.
Mr Walsh said of Heathrow: "The airport's baggage system cannot process all of the passengers' bags and where passengers have been able to check their bags in, the lengthy queues in the airport security search area means that passengers are unable to get to the departure gate in time for their flight."
Mr O'Leary said: "Ryanair and other major UK airlines cannot keep cancelling flights and disrupting the travel plans of tens of thousands of British passengers and visitors solely because the BAA cannot cope with the new body search requirements.
But Mr Douglas told the BBC: "If this is maintained we are likely to continue to see extremely long queues and regrettably even more flights cancelled.
"Quite simply I don't know how long it's likely to go on, but it's clearly a set of measures that are unprecedented and by virtue of what they've come in to enforce, they're not sustainable measures."
Last night thousands of passengers were expected to be left stranded at Heathrow after BA said no more short-haul passengers would be checked in yesterday and some flights would fly to their destinations without passengers to ensure they were in the correct position for today.
A Department for Transport spokeswoman they had not received any direct request for extra security staff from either BAA or Ryanair.