What do these airplanes do if the pilots don't do anything after the cleared route is programmed in? Does it fly any clearance limit and hold? If you are cleared to the destination airport will it just shoot an approach or hold at the IAF, or something else altogether?
Recall what the 737-200 actually did.
Flew to Athens, then took to circling at a cruise altitude. When one engine quit due to fuel exhaustion, the plane did not fall off the sky immediately, but the door lock opened, so a PPL could get in.
How would your 747 or 767 act in stead of that 737?