The number of passengers travelling on transatlantic flights from the UK's leading airports dipped sharply after the September 11 terrorist attacks.
The British Airports Authority says North Atlantic traffic at its seven UK airports was down 25.9% in September, and down 38% between the 12th and the 30th.
Other long-haul traffic fell by 6.8% compared with the same month last year.
The company has issued full statistics after releasing 'headline' figures ahead of time last week.
BAA operates Heathrow, Gatwick, Stansted, Southampton, Glasgow, Edinburgh and Aberdeen airports, which handled 11.2 million passengers last month - 6% fewer than in September, 2000,
For the first 10 days of September, numbers were up 3%, but they dipped by 10.6% following the terror attacks.
Passenger numbers at Heathrow fell by 13% for the month - being 0.7% down even before the terrorist attacks, and then dropping by 19.7% afterwards.
Gatwick fell 6.2% for the month - being 0.6% up before September 11, and 10% down after; Southampton had a 2.2% fall; but Edinburgh rose 13.4%; Stansted was up 11.4%; Glasgow increased by 6.9%; and Aberdeen rose 0.6%.
There were gains for the month in domestic traffic, up 0.9%; European charter passengers (up 1.4%); and Irish traffic (up 1.9%).
Cargo tonnage fell by 22.2% in the month - being down 11.9% before September 11, and falling by 27.5% afterwards.