Last year airports in Britain handled 17m fewer passengers than in 2008, according to the Civil Aviation Authority (CAA).
The 17% slump was a return to air passenger figures seen in 2004 levels, and represented the largest annual decline for 65 years.
It was also the first time figures had fallen two years in a row.
Harry Bush, CAA's director of economic regulation, said: "Today's figures show the biggest fall in passenger numbers since the second world war, highlighting the enormous impact the recession has had on the aviation industry.
"Passenger numbers are now back to the level they were six years ago and, 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."
By the end of 2009 there were signs of improvement, however, with the rate of decline slowing from 12.5% in Q1 (compared to the same period in 2008), to 3.8% in Q4.
The CAA also reported regional airports were worse affected than those in London.
At London airports the fall in traffic was 4.9%, while for airports outside the capital contracted by 10.7% on average.
During 2009 total air transport movements (landings and take-offs by commercial aircraft) at UK airports fell by 8.8% to 2.1m, which is the largest annual fall since the 1940s.
www.caa.co.uk