A "significant" number of holidaymakers are still without their luggage as British Airways continues to recover from the chaos caused by a major system failure.
The airline said its IT systems are "back up and running" and it was operating a full schedule on Tuesday but apologised to those who had not been reunited with their bags.
Travellers getting away for half-term breaks were stranded at airports over the bank holiday weekend and have been forced to start their holidays without their baggage.
In the latest update for passengers on its website, BA said: "Although we have already flown many bags to the correct airport, there is still some work to do and we know there are still significant numbers of customers who are yet to receive their luggage."
Passengers left without luggage are being advised they can claim money back for essential items.
A BA spokesman said: "We are very sorry for the frustration customers are experiencing and understand the difficulties they are facing.
"We're working round the clock to reunite customers with their luggage. We are delivering bags to customers, at homes or hotels, as soon as the bags arrive at their final destination.
"Customers can update their personal details or check the very latest status of their bag delivery on ba.com."
Experts predict the knock-on effect of the IT outage could continue for several days and BA is facing huge compensation costs, with reports suggesting the bill could top £100 million.
The airline's parent company, IAG, saw shares fall by around 3% in the first day of trading in London after the problem emerged.
Shares in IAG, which is also listed in Madrid, had already tumbled heavily in trading in Spain on Monday, wiping around 410 million euro (£357 million) off the stock.
BA has said there is no evidence it was the victim of a cyber attack and added the cause of the IT issues was a surge after "total" power failure.
The spokesman said: "It was not an IT issue, it was a power issue. There was a total loss of power.
"The power then returned in an uncontrolled way, causing physical damage to the IT servers.
"We know what happened, we are investigating why it happened."
BA chief executive Alex Cruz has promised a full investigation into the failure, which affected 75,000 passengers as thousands of flights were cancelled.
He said: "On Saturday morning we did have a power surge. It did affect our communications systems.
"We are now focusing on making sure everyone's needs are addressed. We will make an in-depth investigation to make sure we get to the bottom of exactly why this happened and we will react.
"Absolutely this will not happen again at British Airways."
On Saturday night, travellers spent the night sleeping on yoga mats spread on terminal floors after BA cancelled all flights leaving the London hubs, while disruption continued into Sunday with dozens more services from Heathrow axed.
The IT outage had a knock-on effect on BA services around the world, while passengers who did get moving on the limited number of flights to take off from the UK reported arriving at their destinations without their luggage.
Mr Cruz said the outsourcing of jobs was not to blame for the "catastrophic" IT failure.
BA was accused of greed after the GMB union suggested the disruption could have been prevented if the beleaguered airline had not cut "hundreds of dedicated and loyal" IT staff and contracted the work to India last year.
Low-cost carrier Ryanair described the disruption as a "disaster" for BA and poked fun at the airline on Twitter.
Ryanair reported a surge in bookings for last-minute travel over the weekend as BA customers were forced to make alternative arrangements after their flights were cancelled.
BA has come in for criticism after signposting some customers to a phone line costing up to 62p per minute.
BA's Twitter account suggested a number of passengers should call 0844 493 0797 - which can cost up to 7p per minute plus an access charge of up to 55p.
The airline said it has a freephone number - 0800 727 800 - for people affected by the IT failure.
A spokeswoman said: "As a global airline that flies to and from more than 170 airports worldwide, we have call centres placed strategically around the world in the UK, Europe and Asia.
"Customers can also add phone charges into any claims they submit and we'll look at them."
Asked about the BA meltdown at an election campaign press conference in Wolverhampton, Prime Minister Theresa May said: "The IT crisis that hit British Airways is predominantly a matter for British Airways.
"I recognise the considerable disruption and problems it cost for all those individuals who had been hoping to get away for their holiday and for their break and found themselves stuck in airports and unable to travel, and I think we all feel for those people.
"It's up to them to sort their IT out and to ensure that they are able to provide the services that people expect them to provide as British Airways."