The subject matter of this specification can be embodied in, among other things, a method that includes generating a first graph including possible flight segments between airline stations for an airline and determining a set of permissible crew pairings based on a traversal of the first graph. The method also includes generating a second graph comprising the determined set of permissible crew pairings and determining a set of permissible aircraft routings based on a traversal of the second graph. The method includes generating a set of optimized aircraft routings using an integer-programming algorithm that accepts the determined set of permissible aircraft routings as input, and outputting the set of optimized aircraft routings for use in a flight schedule.