I remember a couple years back being on an AA 767 to LHR, and seeing the Concorde takeoff in front of us on RWY31L. This would make sense as 31L/13R is the longest runway. It seemed to me that this was the only runway available for the Concorde at JFK since it is the longest. Is this true, or can it also go off 4L/22R, the second longest runway? Also which runways are used the most for the departure?