The accelerometers in consumer grade drones are not nearly accurate enough for inertial navigation over any significant distance. Satellite navigation is often jammed in war. The US military can degrade the accuracy of civilian GPS signals without affecting the encrypted military signals. Frequency hopping can work around some jamming, but a powerful enough jammer will overload and desensitize the receiver making it unable to hear anything.

Optical based navigation would be immune to RF jamming, but that’s not going to be found in consumer grade drones.