The recession has had an "enormous impact" on the aviation industry
UK airports have suffered their biggest decline in passenger numbers since records began at the end of WWII.
They handled 216.8m passengers last year - 7.4% fewer than in 2008 - the Civil Aviation Authority (CAA) said.
The recession in 2008 and 2009 represented the first time that passenger numbers had fallen for two successive years, CAA figures showed.
CAA economic regulation director Harry Bush said the numbers would "rebound" but the pace of recovery was uncertain.
He said the large decline highlighted the "enormous impact the recession has had on the aviation industry.
"Passenger numbers are now back to the level they were six years ago.
"Although they will certainly rebound, the pace of recovery is uncertain and it could be a number of years before they reach their peak level again," he said.
Heathrow decline lowest
Charter airline numbers saw the biggest drop - a fall of 17% - while UK domestic flight traffic was down by 8% and scheduled airline traffic fell 6%.
Much of the overall passenger decrease came in the first part of 2009, with numbers down 12.5% in the January-March quarter.
The decline in the final three months of last year was only 3.8% compared with October-December 2008.
The decline at five airports in the London area - Heathrow, Gatwick, Stansted, Luton and London City - was 4.9% overall.
The largest declines were at London City (14.2%), Stansted (10.7%) and Luton (10.4%).
Heathrow had the smallest decline among London airports, handling 66m passengers in 2009 - just 1.5% fewer than in 2008.
Gatwick handled 32m passengers - a 5.3% fall on 2008.
At airports outside London the traffic last year fell by 10.7% to 88m.
Manchester, the largest regional airport, saw passenger numbers plunge by 11.5% to 2.4m, while at Birmingham airport they dropped by 5% to 483,000.
During 2009, air transport movements - landings and take-offs of commercial aircraft - at UK airports fell by 8.8% to 2.1m, which is also the largest annual drop since the 1940s.
In 2008 passenger numbers fell for the first time in 17 years, with an overall decline of 1.9%.