[Bloody Sam Roberts]

I would think that in order for this Lear aircraft to go straight in at 600mph it would need to be under near full power to do so.

This might indicate a pilot health issue. But from 28000 feet, how could a co-pilot or someone else not respond and right the aircraft?

Unless the pilot was healthy and locked everyone out of the cockpit intentionally. Just speculating.

[Dan Nunn]

Unless the pilot was healthy and locked everyone out of the cockpit intentionally. Just speculating.

At 600mph, does the cockpit need to even be locked to keep anyone out? I doubt anyone is able to fight gravity and make it to the cockpit.

[rainee]

At that altitude, wouldn’t the Lear be cruising/autopilot?
& then to descend at that speed into nosedive? If engines were running, then what else might possibly be the cause?
Pure terror those last few minutes/seconds...

[Bubba Ho-Tep]

I would think that in order for this Lear aircraft to go straight in at 600mph it would need to be under near full power to do so.

That's the speed that it's estimated Payne Stewart's plane hit at, and it was out of fuel.