The British Airports Authority (BAA) experienced a 22.7% fall in passenger traffic in April year-on-year due to the recent volcanic ash crisis.
BAA said its six airports in the UK handled 6.9 million passengers last month, compared with nine million in April 2009.
Heathrow airport handled 4.4 million passengers in April, which is a 20.8% decline compared with the same period a year ago.
Stansted airport recorded a 24.4% fall, while Glasgow airport reported a fall of 29.2%.
In total, the group recorded a decrease of 21% in the number of air transport movements during April.
Cargo tonnage increased by 6.2% compared with last year, despite the disruption.