I did some research on this a few years ago. There is also a thread on this in the archives. As Vipes has said, generally due to winter weather systems its more common for planes to use the westerly preference ie fly from east to west over the Biggin Hill stack then over Forest Hill from the spring onwards. This is why we seem to notice it more around April time, and of course we all start opening our windows at this time of year so notice it even more. The extent to which individuals notice or are bothered about it varies a great deal. I noticed it more when I moved out of a (noisy) block of flats into a quieter house on a relatively quieter road. It has however definitely increased in the last few years, and our family and friends comment on it when they come to stay. Personally I am less affected by the City Airport flights which I see as no more disturbing than a passing car.

We clearly don't want to become Luddites but air traffic noise clearly is a problem thats going to increase for all Londoners in the coming years, even in the outlying eastern/southeastern suburbs, so we either need to start getting used to it or finding something that we can realistically do to effect change. Homes and businesses on the flight path nearer to Heathrow can claim allowances for additional sound insulation so this might be one thing to start demanding.