Hundreds of passengers were stranded overnight
Dozens of flights in and out of Heathrow Airport's brand new £4.3bn Terminal 5 have been cancelled and staff are dealing with a backlog of 15,000 bags. But what caused the baggage-handling system to break down on that fateful first day?
Despite months of preparations at T5, its problems began almost immediately as staff arrived for their morning shifts.
Many British Airways airport workers complained they were delayed getting to the building because of a shortage of specially-designated car parking spaces.
Some also reported that staff overflow car parks were not open and they had been forced to drive around in circles to find somewhere to put their cars.
Then, once inside the terminal building, workers also faced problems getting to the restricted "airside" via security checkpoints.
Jamie Bowden, an aviation analyst and former BA customer services manager, was at T5 during the early hours on launch day and said he began to have concerns when he saw queues of staff.
European and short-haul flights operated on a tight schedule, he said, and staff needed to "hit the ground running" to ensure everything ran on time.
"I thought 'Woah! There are a lot of people not getting to their areas in time'. If I had seen this in Terminal 1 it would have immediately signalled danger to me.
"If you start the day like that you are playing catch-up all day long."
As well as being delayed getting through security, many staff were also unfamiliar with the building and systems they were using.
Ed Blissett, from the GMB union, reported how workers had not been familiarised with the new terminal and that many "didn't know where to go, what bags to get".
One baggage handler told the BBC it was "a shambles the moment the doors opened" and blamed BA for the "lack of training and the essential support that was promised".
A check-in attendant with 10 years' experience also told the BBC: "It took an hour for people to get to the right place. The place is so enormous, we don't know where we are going, we've been given no maps, no numbers to ring."
Other staff reported that, due to poor morale, many had not attended training courses and trial runs.
Another flight cabin service director, who has more than 15 years' experience, also claimed there were not enough people working at T5 on opening day.
"They asked for volunteers to make up numbers at T5. I don't know anyone who would go and volunteer on their day off," he said.
"Whenever in the past BA got into a mess, people helped out, but morale is so low people won't do it any more."
Once staff working that morning were in position, some workers in the baggage sorting area reported not being able to log on to the computer system, while others struggled to use the Resource Management System (RMS), which allocates handlers to load or unload flights.
"They were in a position where they were unaware of what tasks they had been given," said Mr Bowden.
But despite the confusion behind the scenes, check-in staff continued to add luggage to the system, which is designed to handle 12,000 bags an hour.
This then led to "meltdown", said Mr Bowden, with bags clogging up the underground conveyor system because baggage workers were not removing them quickly enough at the other end.
By Thursday lunchtime the cumulative effect of the staff problems meant BA had to cancel 20 flights. By about 1700 GMT the airline was forced to suspend all hold luggage check-in to try to clear the backlog of bags.
BA chief executive Willie Walsh accepted responsibility for the chaos
This meant passengers already at the airport had the choice of either flying with just hand luggage, getting an alternative flight or claiming a refund.
By the end of T5's first traumatic day, a total of 34 flights had been cancelled and hundreds of passengers had been left stranded.
By Saturday, BA said it had a backlog of at least 15,000 bags at Heathrow - with one source telling the BBC that the number may have been closer to 20,000.
BA has already said "teething problems" with car parking, delays in getting staff through security screening and staff familiarisation resulted in the backlog of baggage which led to the severe delays and flight cancellations over the days that followed.
But, according to Mr Bowden, the airline's bosses had been warned by staff they were not fully prepared for the transition to T5.
"Many areas of BA had told their managers month after month that they were not ready to move in or didn't feel confident to move in - but there was a general feeling of hubris - 'Don't worry, it will be okay on the day'."
He added: "Essentially, people didn't feel familiar with the terminal, were
under-trained and didn't understand the geography."
PROBLEM AREAS AT TERMINAL 5 ON THURSDAY
1. 0400 - Both passengers and staff have trouble locating car parks
2. 0400 - Delayed opening of check-in results in long queues
3. 0442- First passengers arrive early but wait an hour for luggage
4. All morning - Clogged conveyor leads to long wait for luggage
5. 1630 - Baggage system failure; all check-in at T5 suspended
6. 1700 - After long queues form at "fast bag drop" desk, BA suspends check-in of all luggage into hold