BAA said Heathrow, Europe's busiest airport, handled 65.7 million passengers in 2010, down 0.2%. Without the disruptions, BAA estimated that Heathrow traffic would have grown by 3.4%.
The snowstorms which snarled traffic in late December knocked £19m off profit at Heathrow, BAA said.
Snow grounded aircraft at Heathrow on December 18 and the second runway was out of action until December 21.
Hundreds of flights were canceled and travelers were stranded for days.
"The cost of any disruption to BAA's airports is significant and a strong financial incentive for us to continue to make Heathrow more resilient," said company CEO Colin Matthews. He has said he won't accept a bonus for 2010 in response to the problems at Heathrow.
Matthews has commissioned an independent investigation of December's problems at Heathrow. Virgin Atlantic Airways announced earlier this week that it would withhold airport fees until that report is published, probably in March.
Traffic through Heathrow also was hit by the volcanic ash cloud from Iceland's Eyjafjallajokull volcano that prompted the cancellation of about 100 000 flights worldwide. Heathrow and BAA's London Stansted airport were closed from April 15 to April 20.
Two strikes by British Airways cabin crew during the year also caused many flight cancellations.
BAA, owned by a consortium led by Grupo Ferrovial of Spain, also owns terminals at Southampton, England; Glasgow, Aberdeen and Edinburgh in Scotland; and Naples, Italy.
Traffic at all the British airports fell. Stansted was down 11% in December and 7% for the year. The Scottish airports saw traffic drop by 15.5% in December and 7% during the year.
Naples traffic, however, was up 5% for the year.