When I was talking to Justin, G4TSH on the phone the other evening, he was playing me the 50MHz GB3RAL signal and it was interesting to see just how many aircraft reflections there were from the signal. It would come up to a reasonable strength and then fade away again - but allowing plenty of time for identification of the signal to take place.
Certainly if you live anywhere near Heathrow Airport with a very active airspace, there's plenty of opportunities for some interesting contacts. When I lived in Windsor, one of the most memorable contacts I made was with Stewart, GM4AFF on 2m via aircraft scatter, but working GD0EMG on both 4 and 6m was fun too. You had to time your QSOs very precisely and if someone wasn't quite slick enough you could very easily lose the QSO.
Anyway - mention of aircraft scatter is just a front to allow me to post a video of the RAF flypast across London today, celebrating 90 years of the Royal Air Force. Tower Bridge is just down the road from work, so we popped down there at lunchtime to see the event.