Passengers faced a third day of disruption at Heathrow on Monday as British Airways cancelled short-haul flights after a global computer crash that unions blamed on the outsourcing of IT services to India.
The embattled airline said it was cancelling 13 short-haul flights from Heathrow Airport, Europe's busiest, but was aiming to operate a full long-haul schedule from the hub and was operating a full service from Gatwick Airport.
Tens of thousands of passengers were left stranded over a busy holiday weekend in Britain after BA scrapped hundreds of flights worldwide.
The knock-on effects could continue for several days.
The airline urged passengers on Monday to check their flight status online before travelling to the airport in a bid to avoid scenes seen over the weekend when people camped out at Heathrow overnight.
BA chief executive Alex Cruz told the BBC he would not resign over the disruption and said it had nothing to do with cutting costs.
He said it had been caused by a power surge that had "only lasted a few minutes" but the problem was that the back-up system had then not worked properly.
The GMB union, however, said the disruption "could have all been avoided" if BA had not cut hundreds of IT jobs in Britain and transferred the work to India.
The airline said it was making "good progress" on restoring normal service.
"As our IT systems move closer to full operational capacity, we will again run a full schedule at Gatwick on Monday and intend to operate a full long-haul schedule and a high proportion of our short-haul programme at Heathrow," a spokeswoman said.
"We apologise again to customers for the frustration and inconvenience they are experiencing and thank them for their continued patience," she said.
Cruz said that 75,000 passengers had been affected.
"We know that there have been holidays interrupted and personal events that have been interrupted and people waiting in queues for a really long time," he told Sky News.
"We absolutely profusely apologise for that and we are absolutely committed to provide and abide by the compensation rules that are currently in place."
Shares dropping
Some British media suggested Monday that BA could be hit with a bill of more than £100 million (115 million euros, $128 million) for compensation costs for stranded passengers' food and accommodation.
BA cancelled all its flights out of Heathrow and Gatwick on Saturday after the IT failure, which shut down all of the carrier's check-in and operational systems and affected call centres and its website.
Passengers were asked to contact BA to locate their luggage, after many were forced to leave Heathrow without claiming their bags in chaotic scenes that saw queues snaking out of the airports.
BA's outage came on a busy weekend in Britain, where Monday is a public holiday and many schoolchildren are beginning a week's holiday.
British Airways has suffered other IT glitches recently, leading to severe delays for passengers in July and September last year.
IAG, the parent group of British Airways and Spanish carrier Iberia, earlier this month reported a 74-percent slump in first-quarter net profit to 27 million euros ($30 million), due in large part to a weak pound.
Shares in IAG on the Madrid stock exchange are currently trading down by about 2.5 percent.
Explore further: More Heathrow chaos as BA scrambles to recover from IT crash (Update)