British Airways has cancelled all flights in and out of Heathrow until Friday evening because of unofficial strike action by ground staff.
The chaos was prompted when 600 catering staff were sacked
Some 70,000 passengers, many of them stranded, will be prevented from travelling until 1800 BST.
BA grounded all flights after hundreds of baggage handlers, ground staff and loaders took unofficial action in support of 600 sacked catering staff.
A further five airlines have been affected by the disruption.
These are Sri Lankan Airlines, Finnair, GB Airways, British Mediterranean Airlines and Qantas, which are also serviced by BA ground staff.
Earlier talks with the Transport and General Workers Union aimed at reinstating 600 sacked staff from the caterers that serve BA flights, Gate Gourmet, broke down without agreement.
BA chief executive Rod Eddington apologised to passengers and called for more talks to begin urgently between the TGWU and Gate Gourmet.
The catering firm said the door was open, but the union said it could not see a way forward.
Out of place
Sir Rod said BA was forced to cancel so many flights because it did not have "sufficient airport staff to operate flights into or out of Heathrow".
Some 70,000 passengers are affected by cancellations
Nearly 100 BA aircraft and 1,000 pilots and cabin crew are in the wrong places around the world, he said.
"We simply cannot mount a robust operation any earlier.
"It is a matter of huge disappointment that we have become embroiled in an issue which is not a dispute with British Airways and disrupted thousands of people who were about to take their hard-earned summer holidays.
He urged the TGWU to encourage its members "to put our customers first and go back to their work places".
The dispute began when Gate Gourmet dismissed 600 staff after an unofficial strike on Wednesday over the company's restructuring plans.
This led to a shortage of catering supplies on BA flights, and a decision to ground all Thursday's flights and divert 14 inward-bound flights followed.
The dispute escalated when hundreds of BA baggage handlers, loaders and other ground staff represented by the TGWU staged an unofficial secondary walk-out. BA said there was little it could do as the walk-out was related to a dispute outside its control.
A spokesman said of the situation on Thursday: "We are trying to get people home and trying to find hotels for those who need one."
He urged passengers due to travel on Friday not to turn up at the airport, but to contact the airline or their travel agent to arrange a refund or to rebook their travel plans.
Waiting on pavements
On Thursday, hundreds of confused passengers crammed on to floors inside the Terminal Four departure hall.
And loudspeaker announcements asked anyone not flying to leave the building as staff closed the main doors to prevent overcrowding, leaving hundreds more waiting on the pavements outside.
AFFECTED AIRLINE NUMBERS
0800 727 800
0870 000 0123
Sri Lankan Airlines:
0208 538 2000
0845 758 1111
0870 850 9850
British Med Airlines:
0870 850 9850
BBC correspondent Russell Hayes said the TGWU recognised the walk-out by BA staff was illegal "wildcat" action and was trying to persuade members to go back to work.
Gate Gourmet has said it will not re-instate staff and said it had told the TGWU it was facing a financial crisis.
It said the actions of the staff had jeopardised the livelihoods of the entire 2,000-strong workforce.
Gate Gourmet's Andy Cook told BBC News before Thursday's talks: "We are in the situation at the moment where we need to make changes.
"We really do want to do that with the cooperation of the union and the staff, but we have to manage the business otherwise it will cease to exist."
But the TGWU said managers had provoked the dispute and the union was taking legal advice.