The statement came on the day the struggling UK flag carrier said it was scrapping or suspending 190 services, including 36 flights to the United States and its Heathrow-Belfast route.
And BA executives, including chief executive Rod Eddington, have agreed to a 15% pay cut to help the airline through "these most difficult times".
Last week, BA had said it was cutting 7,000 jobs and reducing capacity by 9%, partly because of the crisis in the global aviation industry following the attacks.
Most major airlines have also cut back schedules substantially. More than 100,000 job losses have been announced.
Belfast jobs lost
In its latest announcement, BA said it was suspending flights between Gatwick and New York's JFK airport and withdrawing its Heathrow-Belfast service.
About 160 jobs are expected to be lost with the closure of BA's operating base at Belfast International Airport.
TBI, the company which operates the airport, said the action meant its pre-tax profits would fall £1.6m this financial year and £5.3m the following year, in the worst case scenario.
'Difficult conditions'
BA said its total revenue was reduced by £48m in the two weeks after 11 September while transatlantic traffic dropped 60% in the week following the attacks.
It said the £40m figure included costs related to operational disruption and implementation of immediate security measures.
For its last financial year, BA reported operating profit of £380m.
"The current difficult market conditions demand we take firm action. Our focus has to be on making best use of our assets," said BA's director of strategy David Spurlock.
Transferred
Most of the cutbacks centre on flights to the US.
As well as suspension of the daily flight between Gatwick and JFK, there will also be a reduction of one daily service from London Heathrow to both JFK and Boston, and fewer flights a week to Washington.
Middle East services are also being reduced.
Some other services have been transferred from Gatwick to Heathrow to improve profitability.
Massive cutbacks
British Airways is not alone in having to make cutbacks following the attacks on the US.
US and Canadian airlines have announced more than 100,000 job losses, which they have blamed on the attacks.
On Wednesday, US carrier Delta said it was axing 13,000 jobs and reducing capacity by 15%.
Air Canada also blamed the downturn in trade since the attacks for a decision to cut 4,000 posts.