Someone asked about when the busiest time for Heathrow is.
1 plane lands and takes off every minute for pretty much the entire day expect the dead of night. Apparently the locals don't like jumbo's a few feet from there bedroom whilst trying to sleep

Sat on the tarmac at night the stream of planes coming in looks about right for reality.
I used to sit on a hill in Guildford watching the same sight along with the similar into Gatwick. Fantastic view point!
I think where Heathrow wins is that it has the busiest airspace. Along with Heathrow, the London area has Gatwick, Stanstead and London City flights along with most flights between the US and Europe passing higher through the airspace.
There is always lots of ai traffic around here. Try the airspace just West of Heathrow towards Farnborough atc is scatering planes in all direction as I fly wherever I wish to ;D
Lastly, on my very first flight in FS2k4 I was made to circle for 10 minutes above Heathrow and then when I was called myself and the plane I was 1 minute behind got sent around due to an airliner being stuck on the active runway. Now that I liked. I could see the newspaper reports already!
I only have ai flights on medium settings.
Kev