Luggage check-in was suspended on the opening day
The chaos that marred Heathrow's Terminal 5 on its opening day, leaving many stranded overnight, "was not our finest hour" BA's boss has admitted.
British Airways' chief executive Willie Walsh accepted the debacle had affected the reputation of BA and of Britain.
More than 100 flights were cancelled on Thursday and Friday with another 54 flights on Saturday cancelled.
Airport operator BAA said it was working with BA to resolve the severe baggage problems.
A BAA spokesman said: "BAA's first duty is to passengers and airlines.
"Today at T5, we are focusing all our efforts on our work with British Airways to resolve baggage issues and to deliver a good service to passengers. Elsewhere at Heathrow, our terminals are working normally."
Mr Walsh said the situation was improving on Friday, but admitted the opening was not a success.
"We clearly disappointed a number of people and we sincerely apologise."
He said a "combination of factors" that they had been unable to "get on top of" had led to the disruption.
"British Airways has not delivered and we need to deliver," he said. "I am accepting responsibility, the buck stops with me."
He said: "Today has started much better," but added: "At this stage I still expect some cancellations tomorrow".
He told BBC Radio 4's World At One programme that if one of the numerous hold-ups - including staff car-parking problems, staff security screening and baggage delays - had happened "in isolation", then the resulting travel chaos would not have been so severe.
He described the baggage delays as "minor system problems" and said that as the system had undergone six months of testing "we should absolutely have done better".
"In isolation some of these problems were identified and we felt they had been addressed. There were some basic human errors made that compounded the problems."
Late on Friday the airline cancelled 54 flights to and from Heathrow on Saturday, while 293 flights remained on the schedule.
It followed the cancellation of 36 of Friday's flights from T5 and 36 to the terminal.
The airline advised customers to check its website, www.ba.com, for service updates.
Passengers could now check-in both hand and hold luggage.
The airline, which has sole use of T5, says it has drafted in extra staff and held meetings through the night to try to ease the problems that wrecked the terminal's first day.
Some stranded travellers spent the night on the floor of the new building.
The suspension of luggage check-in was not the only problem to hit passengers hoping to leave T5 on its opening day.
Earlier in the day BA announced that "initial teething problems" with car parking provision, delays in staff security screening and staff familiarisation had resulted in a backlog of baggage.
A further technical fault also meant seven flights left T5 without luggage on board.
Sources have also told the BBC that morale was low among staff.
One baggage handler told BBC News what should have been BA's greatest hour had "turned into a shambles the moment the doors opened".
"BA claimed 'staff familiarisation' was to blame. The staff, however, would blame the lack of training and the essential support that was promised," he said.
"During the inadequate training days prior to the opening, any staff questions were bounced back with 'I don't know' and 'It will be clear on the day'.
"Staff signage is non-existent and quite frankly, how are we expected to help customers if we are not helped first?"
BBC reporter Steve Rosenberg said on his flight from Berlin to Heathrow the captain warned passengers that "things haven't been going well at Heathrow, so keep your fingers crossed".
On arrival, there was a delay while ground staff were found to help park the plane, and there was no bus driver available to collect the disembarking passengers.
More than 70 flights were cancelled on Thursday and Friday
Once at the terminal door, there were further delays as a swipe card used to open it would not work. But our correspondent said his bags came through on the conveyor belt promptly.
The BBC's transport correspondent Tom Symonds said the backlog was caused by problems with the airport's luggage processing system.
An underground conveyor system had become clogged up, he said.
This was being blamed on staff failing to remove luggage quickly enough at the final unloading stage.
Passengers on Thursday's cancelled flights were offered £100 towards the cost of overnight accommodation by the airline, but travellers reported that local hotels were charging up to twice that figure.
David Frost, director general of the British Chambers of Commerce, said the "shambles" had sent a "depressing message to businesses around the world".
"This is a PR disaster at a time when London and the UK are positioning themselves as global players. We can only hope that this will provide a wake-up call as we gear ourselves up to host the Olympics in 2012."
BA has set up an information line for T5 passengers: 0800 727800
Have you been through Terminal 5 today? What was it like? Do you work there? Tell us about the new terminal at Heathrow airport.
You can send pictures and video to: firstname.lastname@example.org or to send via MMS please dial +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.