Passenger traffic at BAA's six airports dropped 1.5% year-on-year in March 2010, following seven days of strikes by British Airways' cabin crew.
BAA's UK airports handled a total of 8.2 million passengers in March, compared with 8.4 million in the same month last year.
Heathrow was expected to have recorded a growth of 3.8% on last year's figure, while the group as a whole was estimated to experience an increase of 1% before the strikes took place.
Traffic dropped 9.6%, 3.3% and 4.4% respectively at Glasgow, Edinburgh and Aberdeen, each airport experiencing an estimated 1% to 2% loss of traffic due to the strike.
Passenger traffic at Stansted declined by 4.2% compared with last March, while it rose 5.3% at Southampton and 5.7% at Naples.
European scheduled services increased 0.1% and North Atlantic traffic by 1.7%.
Long-haul traffic rose 0.5% overall with services from Heathrow to China increasing by 10.9%, the Middle East by 7.2% and South America by 6.8%.
There was a drop of 6.8% in domestic traffic and 6.6% in air transport movements in March 2010.
Cargo traffic saw a growth of 27.7% in tonnage at group level and a 29.6% increase at Heathrow.