British Airways PLC said on Tuesday that the terrorism scare last month that grounded several of its flights cost the airline 40 million pounds.
The carrier said the extra expense came from lost revenues - it cancelled around 1,280 flights during the height of the alert - and the cost of hotels, catering and baggage repatriation for passengers whose flights were cancelled.
The airline added that there had been some impact on forward bookings since the disruption, largely because of ongoing heightened security measures at Britain's airports.
However, overall passenger numbers were still up in August compared with 2005, rising 1.5 per cent to 3.15 million.
"The overall level of bookings has returned to levels experienced in 2005, but is still weaker than the trend of the past few months," BA said in a statement.
"The recovery of premium and non-premium transfer traffic, for example, is lagging due to the limitations on carry-on baggage at London."
BA is the first airline to reveal a cost estimate for the alert that crippled the country's airports last month.
In comparison, a week before the alert, the carrier announced a first-quarter net profit of 150 million pounds on revenue of 2.32 billion pounds.
BA is among several airlines that blamed BAA PLC for the chaos that followed the alert, claiming the airports authority was ill-prepared for the emergency.
BAA has defended its actions.
Budget airline Ryanair Holdings PLC, meanwhile, has blamed the government for its own loss of revenue and has launched legal action in the High Court, claiming 3 million pounds in compensation.
Looking ahead, BA said "visibility" about trading was limited as it emerged from the issues surrounding August's alert, but added that market conditions continue to be good.