After how many minutes can a flight take off before the flight which has taken off?

Answer 1

Immediately but there is a danger of getting into "bad air". The separation is not controlled in 'minutes' but in distance between the two aircraft. Here are the rules from pilot training:

* Category I

light-weight single-engine propeller driven aircraft * Category II

light-weight twin-engine aircraft weighing 12,500 pounds or less * Category III

everything else including high performance single-engine propeller air-planes, large multi-engine propeller aircraft and all turbine powered aircraft The FAA separation regulations also specify that departing aircraft may not take off from a runway unless: * A landing aircraft has taxied clear of the runway, or * A departing aircraft is airborne and is clear of the departure end of the runway or * A departing aircraft has turned away from the departing runway But the regulations also say that the following aircraft can depart: * If the take-off separation is 3,000 feet and both aircraft are Category I * If a Category II aircraft departs before a Category I aircraft * If a Category II aircraft takes off after a Category I aircraft * If both aircraft are Category II aircraft and the separation distance is 4,500 feet * If either aircraft is a Category III aircraft and the separation distance is 6,000 feet from a virtualskies.arc.nasa.gov tutorial (see link)