Charles de Gaulle has 4 runways against Heathrow`s 2 and Gatwick with only 1 is the world`s busiest single runway operation and like Manchester uesd to do before their second runway regularly get
between 50+ movements per hour, but does not air space also have effect
ie having Gatwick, Heathrow, Stansted
Luton plus several other smaller field in a very small area
G-I-B