Bags have been piling up at all Heathrow terminals
Flight cancellations at the new Terminal 5 of London's Heathrow Airport look set to continue for several days.
British Airways called off 37 flights from T5 on Sunday. A further 54 services will not operate on Monday and some may also be disrupted on Tuesday.
The chaos is due to problems with the baggage handling system. About 15,000 bags are stranded across all terminals.
BA said it was working hard to clear the backlog and hoped to increase the percentage of flights taking off.
A total of 208 flights in and out of the terminal were cancelled during T5's first three days. On Sunday, BA said 85% of its 331 scheduled flights were running normally.
The fifth terminal opened amid great fanfare on Thursday, but difficulties with the baggage handling system and with staff training quickly derailed operations.
On Sunday, BA said the system was now "generally working well" and 400 staff members had volunteered to come in on their day off to sort through piles of stranded suitcases.
A team of engineers and IT specialists from BAA and BA are also dealing with problems as they arise.
Bags for UK destinations will be returned by courier, while international luggage will be put on the next available flight.
In a statement BA said: "A backlog of undelivered bags has built up. This backlog is not affecting the day-to-day operation of the baggage system, and we are making every effort to reunite delayed bags with their owners.
"We have more than 400 volunteers from across the airline supporting this effort.
"This work takes time as delayed bags must undergo enhanced levels of security screening. Much of this process has to be done manually because we have been unable to use the Terminal 5 baggage system to process these bags automatically.
"We are sorry for the disruption and inconvenience caused to customers whose flights have been cancelled or whose bags have been delayed."
The company said it and BAA had "invested an enormous amount of time and effort to create Terminal 5", and remained confident that "these early difficulties can be overcome".
But, at the airport on Sunday, some passengers remained critical.
Kerry Johnstone, 35, said she found out only upon arrival at T5, from the electronic board, that she faced an eight-hour delay on a flight to Copenhagen.
"Everyone has to find out when they get here," she said. "It's appalling that such a big organisation has got it so wrong. I can't check in, because they don't know what flight I'm going to be on.
"There was a two-year-old child screaming next to me. When one of the staff tried to make light of it, I said that was exactly what I felt like doing.
"I feel like having a full-blown tantrum but I'm too old."
Government on stand-by
Transport Minister Ruth Kelly said she had spoken to airport operator BAA and BA: "While the problems at Terminal 5 are for them to resolve, I have made clear that the government stands ready to assist.
The CAA has written to BA to ensure it safeguards passengers' rights
"Everything possible must be done to deliver a better service for passengers who are unfortunately still facing disruption and delays to their journeys."
The Conservatives have called for an inquiry into the "chaos and confusion", with Shadow Home Secretary David Davis calling the situation "a dreadful national embarrassment".
Liberal Democrats home affairs spokesman Chris Huhne said the infrastructure project was an "incredible shambles" which "neither British Airways nor BAA seem to be able to put right quickly".
The problems have led BA to consider postponing the transfer of its long-haul operations at Terminal 4 to the new Terminal 5, which had been scheduled for the end of April.
"We haven't said we will alter the original plan," a spokesman said. "But obviously, in the light of what has happened in the last few days, it is prudent to review the situation."
The airline has also faced criticism after initially imposing a £100 upper limit on hotel accommodation costs for delayed passengers.
BA has since said it will consider any "reasonable accommodation cost" claims and the Civil Aviation Authority has written to the company to make sure it complies with European legislation on passengers' rights.
BA has set up an information line for T5 passengers: 0800 727800
Have you been affected by flight cancellations? Has your luggage gone astray in the recent troubles? Tell us about your experience using the form below.
You can also send pictures and video to: email@example.com or MMS to 61124. If you are not in Britain, send your MMS to 44 (0) 7725 100 100
Do not endanger yourself or others, take any unnecessary risks or infringe any laws.
The BBC may edit your comments and not all emails will be published. Your comments may be published on any BBC media worldwide.