Heathrow airport, the UK's largest, had its busiest-ever month in July 2010.
Its terminals handled 6.7 million passengers during the month - a 3.5% increase on July 2009 total, according to airport operator BAA.
But four of the five other UK airports run by BAA saw a fall in passenger numbers in July 2010, compared with the same month last year.
Stansted Airport, in Essex, saw passengers fall 7.2% to 2.02 million.
Meanwhile, Southampton Airport had a 1.4% decrease in passengers to just under 188,000.
In Scotland, Glasgow Airport saw passenger numbers fall by 3.6% to just under 789,000, and passengers at Aberdeen decreased 4.1% to just under 277,000.
But passengers at Edinburgh Airport increased by 0.6% to just over 961,000.
Sunday 18 July was Heathrow's busiest-ever day, when 232,000 passengers passed through the airport.
The six airports handled by BAA saw nearly 58.5 million passengers carried in the first seven months of 2010 - a 4.5% fall on first six months of 2009.