AbstractThis note describes two phases in the development of an expert system that translates European-wide directives into individual flight orders. This expert system was built for a military computer simulation, but parts of the logic can apply—and many of the illustrations in the text have been tailored—to creating and organizing commercial flights. The first phase of the development—a proof of principle expert system—emulated the logical deductions of an air traffic control supervisor or a flight planner. The second phase of development led to a working prototype decision support system that employed more mathematical comparisons of aircraft attributes than logical deductions.