Iran captured a modern US drone using cracking techniques developed through analysis of older crashed drones. First, the drone's remote operators were cut off using electronic noise. Then, once the craft was on autopilot, false GPS signals were sent to it in order to persuade it that it was landing in a safe airbase in Kandahar. The real location was a pre-prepared airstrip in Iran.
Spoofing attacks are serious. Anti-spoofing hardening such as frequent comparison of GPS coordinates to coordinates calculated from inertial sensors and camera images would make this more difficult. Highly accurate inertial positioning systems are in common use in deepwater oil and gas construction equipment, and could readily be adapted to the somewhat less hostile environment of high altitude. Both environments, of course, are subject to currents and other confounders, making them ideal places to share positioning technology.