friend of mine a few years back arranged for me to fly a BA111 sim at Cranebank. I had 30 hours and a PPL. So of course asked him to set me up with the Hollywood scenario; BOTH pilots incapacitated (fortunately, their seats were available).
Plane at 35,000 somewhere over the midlands, on autopilot. So I of course occupied the LH seat, strapped in, put on the headset, decided to transmit a mayday. Presented with the yoke, a button to press on the right, another on the left. So of course, I pressed one, no tranmission. Pressed the other, got a friendly controller who promised to find someone to talk me down.
While waiting for assistance, noticed the altimeter had changed to 29,000. And than to 24,000. Hang on, better add more power here, moved throttles up. This didn't improve the situation. In fact, we rapidly moved down through the airways, until flashing lights and voices urgently saying "PULL UP, TERRAINE, PULL UP TERR.....' and everything went black.
So the cockpit door opened, and the sim operator informed me we were all dead. I had another chance and that time landed at Heathrow, safely. The problem on the first occasion was one button is the transmit, the other one disconnects the autopilot. Dont remember now which was which, so I better stay out of the cockpit.