Flights were grounded at Heathrow in December after more snow fell than anticipated, the airport's boss says.
Heathrow had planned for 6cm (2.4in) "but got far more than that", BAA chief executive Colin Matthews told MPs.
He apologised to the House of Commons Transport Committee for the disruption which saw thousands of passengers sleeping in terminal buildings.
The snow had cost BAA £20m at Heathrow and a total of £24m across its six UK airports, he added.
"In retrospect we should have had a plan for more snow than 6cm," he said.
Operations at Heathrow almost came to a complete halt just before Christmas, with thousands of travellers jamming terminals.
He said BAA had done "all we possibly could" for passengers, but the bad weather "totally overwhelmed the ability of resources at Heathrow to cope with passengers".
Earlier, the committee heard from representatives of British Airways and Virgin Atlantic, who said there had been little communication between BAA and airlines during the disruption.
British Airways operations director Andrew Lord said the weather on Saturday 18 December had "extremely severe" but the airline had expected the second runway at Heathrow to "close and reopen very quickly".
He added: "At the end of the day, if the airport operators do not provide a service to us it is our customers that suffer and that is a situation that is not acceptable to us."
Mr Matthews said: "I am very sorry indeed for the thousands of disrupted passengers and for the thousands of Christmas holidays affected and for the airlines and the company."
He said the company needed to "dramatically improve" its ability to communicate and could "certainly have done better and will do better in the future".
The government is considering new powers to hold airport operators more to account for passenger-related performance.
Mr Matthews told MPs: "I think it would be good to have a sweep of measures to reflect the customer experience and make sure that an airport operator does less well if it performs poorly."
Mr Matthews has announced he will not be taking his 2010 bonus. He ordered an external inquiry into Heathrow's handling of the disruption and the report is expected later this month and will be made public.
Meanwhile, Gatwick Airport chief executive Stewart Wingate told MPs it had had 10cm of snow during the severe weather but had been able to operate again "within five hours".