Disclaimer: This text reflects only the opinion of its author and does not in any way commit the official word of the French Air and Space Academy.
By Jacques Verrière, Full Member.
Since the early days of aviation, we have used magnetic north as a reference for headings and routes, except in the vicinity of the magnetic poles. There are historical reasons for this: until the advent of inertial measurement units and satellite navigation systems (first the American GPS and now the European Galileo system, the Russian GLONASS and the Chinese Beidou), the magnetic compass and flow valves were the only instruments capable of providing a heading reference.
Since then, almost all commercial aircraft have been equipped with satellite navigation systems and, in some cases, with inertial systems. Satellite systems are capable of determining a true course, and inertial power plants are capable of determining a true course and a true course.
General aviation users, on the other hand, are increasingly systematically equipped with instruments that provide a geographical reference.