Even if the technological hurdles could be overcome, which no matter what previous replies have said we are nowhere near to yet!
There is another matter of security, which is more relevant now than ever before. A conventional human crewed aircraft is an autonomous unit.
To gain control of multiple aircraft you need to have a physical presence on each aircraft. Now, if our skies were filled with pilotless aircraft, this would only be economical using a small number of ground control stations for redundancy.
Anyone wanting to create havok would only need to infiltrate / destroy a ground station. Or just interfer with with the comms link to the aircraft.
Ahh, but the aircraft are fully automatic, we don't need ground stations. Yes we do for the following reasons to list but a few:
1) Co-ordination of traffic.
2) Flight monitoring.
3) Fall back for those situations when the on-board automatics can't cope.
This is only the tip of the iceburg.
p.s. No doubt some IT professional will tell us all that we have sophistocated data encryption. There is no data encryption system to date that cannot be broken. Even if the data encryption itself is robust the transmission channel could always be jammed.
These are only some trivial observations / comments, I'm sure the real issues would be even more horrendous.
p.p.s. Keep training, it ain't gonna happen.
My speciality?
Electronics / Automation / Control / Remote Telemetry