To get any appreciable range out of drones they must be large enough to carry a fuel source or an impressive battery bank which would make them large. Doubt these are all predator type drones or amazon delivery level drones flying way out in the country. A fuel driven drone would emit way more than a 'drone like' prop whir. Maybe musk got tired of playing with cars batteries and switched to drones.
Without knowing where the drones came from or where they went, it is impossible to guess the duration of their flight or their potential range.
They have the anti-gravity drive that helps a lot.