Passenger traffic at the BAA airports in the UK declined 0.6% to 10.6 million in August, compared with the same period in 2009.
Heathrow Airport bucked the trend, however, recording its busiest traffic in August and its second busiest month on record, with a 2.5% rise in passengers to 6.5 million.
Passenger traffic declined by 9.4% at Glasgow International Airport, 6.1% at Stansted International Airport, 0.2% at Edinburgh International Airport, 4% at Aberdeen International Airport and 1% at Southampton International Airport.
Cargo tonnage rose by 13.7% at BAA's UK airports, buoyed by a 14.3% increase at Heathrow, although Naples Airport suffered a decline in cargo tonnage of more than 30%.
Cargo traffic at BAA's UK airports increased 2.8% above its pre-recession peak in August.