British Airways chief executive Rod Eddington has admitted the company "got it wrong" after staff shortages led to three days of travel chaos.
Thousands of passengers were left stranded after cancellations
Thousands of passengers had flights cancelled or delayed when check-in desks remained closed on Monday.
Problems continued into Wednesday, despite company assurances that its schedule was back on track.
Rod Eddington said: "Clearly we did get it wrong because we didn't have enough people in the terminal on Monday."
He continued: "We know we're short-handed in the terminals.
"We've got 200-plus people in the training system to address that, but yes, we let ourselves down on Monday night, our customers and our own people."
Almost 90 flights have been cancelled in the past three days, with BA warning that some services may be "merged" in coming days to cope with the continuing staff shortages.
BA office staff have been asked to volunteer to work in the terminals over the Bank Holiday weekend, including Mr Eddington himself.
The airline thought it had avoided any holiday weekend problems when it set a pay deal with check-in staff and baggage handlers, thus averting a planned strike.
Mr Eddington said there was always criticism of BA over whether it was "doing enough to take costs out of our business".
"It's a very difficult balance to get right - clearly we have to get it right."
His admission comes a day after BA's director of operations Mike Street apologised to passengers.
"It was a miserable time for them, we let them down and once again on behalf of BA we're all extremely sorry," Mr Street said on Tuesday.
On Wednesday BA cut seven round-trip flights: two to Glasgow, two to Aberdeen, one to Newcastle upon Tyne, one to Manchester and one to Frankfurt.
BA blamed "ongoing operational difficulties".
A spokesman added: "Our flying programme will be under continuous review over the next few days. We may merge some services to safeguard our operational reliability and robustness.
"If we need to do this the changes will be made well in advance of the departure time to minimise the disruption to our customers."
Problems began on Monday when the airline ditched 50 flights from Heathrow due to technical problems with some transatlantic aircraft and staff shortages.
The knock-on effect of having planes and crews in the wrong place resulted in a further 31 cancellations at the airport on Tuesday.
Earlier on Wednesday, a BA spokesman had said: "The decision was taken yesterday to make four domestic round-trip cancellations.
"These are the last four in terms of tactical cancellations after Monday's disruption."