Re: drones at 000s of feet
The height is plausible, but the regularity is not.
Only high-power remote-camera drones would be pilotable at that height, and not the wifi ones. So the majority of these would have to be uncontrolled or accidental.
A multirotor 'copter has a battery longevity of about 20 minutes. It'll fly for that long, then it will crash.
It is plausible that some owners have lost control and had their copter fly away and 'jam the throttle' (bad failsafe), and as they are self-balanced it could keep climbing rapidly until it reaches a very high altitude ceiling.
It'll stay until the battery goes flat, then it will fall straight down.
A fixed-wing R/C aircraft is also inherently stable, however they generally can't climb quickly and are much harder to fly.
However, there do not seem to be any reports of any drones falling out of the sky, or any drone wreckage being found near where the near-misses are claimed to have occurred.
As nobody has produced that evidence, and it would be very stupid for the CAA etc not to go looking, one assumes that in most cases there was no evidence to find.
So while there probably have been a small number of genuine near-misses with planes and drones, the vast majority of these reports must have other explanations.