BAA saw passenger numbers fall by over a fifth during April, as a volcanic ash cloud from Iceland closed UK airports.
The operator revealed in its monthly update traffic had fallen by 21.5 per cent over the month when compared to expected levels as a direct result of the cloud.
Losses elsewhere meant BAA’s passenger traffic in April was down 22.7 per cent in total on the same month last year.
UK airports were closed for six days during April as ash from the Eyjafjallajokull Volcano drifted across the north Atlantic and Europe.
Southampton and Edinburgh airports were both hard hit, with traffic down by 27 and 26 per cent respectively following closures attributed to the cloud.
London’s Heathrow Airport – the busiest in the country – also saw traffic fall by 21 per cent as a result of the disruption.
Irish airline Aer Lingus also confirmed passenger numbers had fallen during April this morning, carrying over a quarter fewer passengers over the month year-on-year.
The former flag-carrier - which had already been cutting unprofitable services to lower costs and ward off takeover - carried 689,000 passengers over the month, down 27.1 per cent when compared to 2009.
However, the airline’s load factor increased by 1.2 percentage points.
The airline warned earlier this month the initial period of ash disruption could cost up to €20 million.
Following the closure of UK airspace in April, the Civil Aviation Authority (CAA) warned problems may persist throughout the summer.
Further airspace closures were seen across the UK this month, while Spanish airports were closed over the weekend as a result of the ash cloud.
Planes were also grounded for part of the day at airports in Italy, Germany, France, Ireland and Portugal on Sunday.