British Airways today estimated the disruption caused by heavy snowfall and freezing temperatures last month will cost the airline £50 million.
The number of passengers travelling with BA plunged more than 10% last month as airports including Heathrow and Gatwick were forced to close by the adverse conditions.
The airline said the number of passengers carried in December fell to 2.1 million from 2.4 million last year, as its operating capacity was reduced by 12% year-on-year.
The big freeze - the coldest December in the UK since records began - is the latest in a series of events to hit BA's finances.
Flights grounded by the ash cloud emanating from Iceland's volcano cost the airline £108 million, while a series of strikes over the summer set the firm back £142 million.
The £50 million big freeze bill will come as a blow to the airline, which made its first half-year profit for the first time in two years in the six months to September 30.
Thousands of passengers were left stranded around the world last month as Arctic conditions swept across the country, hitting air, rail and road travel, as well as knocking the retail sector.
BA said there would be some small additional impact this month from cancelled return journeys but underlying market conditions remain positive.
The biggest decrease in passenger numbers last month was on BA's European routes, which fell 14.2% to 1.1 million.
But there were declines worldwide, with Africa and the Middle East falling 6.9%, traffic to and from the Americas down 5.6% and passengers to and from the Asia Pacific region falling 6.7%.
BA's planes flew 76.4% full in December - a slight 0.4% decrease on the same month last year.
The airline is set to complete a £5 billion merger with Spanish airline Iberia later this month. The merged airline, which will operate under the parent name International Airlines Group, will have 408 aircraft carrying about 57 million passengers a year.