Wonder what his max ceiling was for his weight - FL260 with 6 on-board, vacation luggage, warmer than standard day, and fuel for Junction City? Might have been unable to make FL260. Got aerodynamic buffet at 25.1 and the stick pusher activated.....
We are talking about a PC12 here. Not a Toy plane.
PC12 47 is capable of full fuel and 7 male people on board.(EASA standard weight incl. handbaggage,)
It can go up to 30000 feet with that weight without any problems, no matter what temperature.
Limiting Factor for the service ceiling of 30000 ft is the cabin pressure, not the plane or the engine.