The dual impact of the Icelandic volcanic ash cloud and British Airways cabin crew strikes hit the number of passengers using BAA airports last month.
The number of passengers through the six UK airports, which include Heathrow, Stansted, Glasgow and Edinburgh, dropped by 4.5 per cent in May to 8.5 million over the same month last year.
BAA estimated that it lost 445,000 passengers to the ash crisis and industrial action at BA in the month.
Heathrow handled 5.3 million passengers in the month, a drop of 3.1 per cent while Glasgow numbers dropped by 13.7 per cent to 560,000 and Edinburgh was down by 11.6 per cent to 726,000.
The number of aircraft movements across all the airports was down by almost five per cent.
Domestic flights saw the steepest decline, dropping by 16.5 per cent over May 2009. The number of charter flights to Europe and North Africa rose by more than five per cent.