An airline wants to conduct a given set of scheduled flights with as few airplanes
as possible. All available airplanes are of the same type. For each flight we
know the departure time and the flight time. We also know, for any pair of
flights i and j, how much time an airplane needs after finishing flight i until
it can begin flight j (this time will depend in particular on where i ends and
where j begins). Show how to compute efficiently a feasible schedule with as
few airplanes as possible.