British Airways was battling its third day of disruption on Monday after a global computer system failure stranded thousands of passengers over a holiday weekend and turned into a public relations disaster.
The airline said it was running a full schedule at London's Gatwick airport on Monday and planned to operate all its long-haul flights from Heathrow, although some short-haul flights had been cancelled.
BA had been forced to cancel all its flights from Heathrow, Europe's busiest airport, and Gatwick on Saturday after a power supply problem disrupted its operations worldwide and also hit its call centres and website.
The disruption continued on Sunday. Some stranded passengers curled up under blankets on the floor or slumped on luggage trolleys, images that played prominently in the media at the start of a week when schools were on holiday.
"Apologises all well and good but not enough. BA has lost another loyal customer #disgraceful," tweeted Tom Callway, who had been due to fly to Budapest.
Spanish-listed shares of parent company IAG, which also owns carriers Iberia, Aer Lingus and Vueling, dropped 2.7 percent on Monday after the outage.
Davy analyst Stephen Furlong said the cost to the carrier of cancelling one day of operations was around 30 million pounds ($38.5 million) in revenue and 4 million in operating profit.
On top of that, the airline will pay compensation to customers for the delays, though he added it looked likely to be a one-off cost which would be limited given the resumption of flights on Sunday and Monday.