Overall the seven handled 11.54m passengers last month, 2.3% fewer than in April 2008.
BAA said this improvement from an 11.3% decline in March was largely due to the change in the timing of Easter, which fell in April this year.
Taking the two months together to eliminate the Easter distortion, the year-on-year decline was 6.8%, in line with the underlying monthly trend recorded since December of 6%-7%.
Edinburgh saw April passenger numbers increase by 3.9% to 752.1k, while Heathrow was up 2.6% at 5.61m.
BAA said both had been bolstered by Easter, while Heathrow had also benefited from an increase in transfer passengers.
Passenger numbers at Gatwick fell by 3% to 2.58m, although the airport held up much better than Aberdeen (-10.7% at 250.7k), Glasgow (-11.6% at 569.4k) and Stansted (-12.6% at 1.63m).
The biggest year-on-year decline was reported at Southampton, where passenger numbers fell by 13.4% to 150.4k.
On a market-by-market basis, long-haul excluding North Atlantic routes was the best performer, with a rise of 1.4% to 2.14m passengers. The only other growth market was European scheduled, which was 0.7% ahead at 5.06m.
Ireland was down 1.7% at 519.5k passengers and the UK/Channel Islands and North Atlantic both down 7.6% at 1.92m and 1.47m respectively.
Worst hit were European charter routes, where traffic dropped 9.9% to 433.1k.
See also:
European airline traffic Apr09 (08/05/2009)
UK bosses urge rethink on third runway (05/05/2009)
BAA sees difficult year ahead [Q1s] (05/05/2009)