This is one of the most violated FARs in the book. The requirement varies for PT91 & 135, single crew or two crew, and if you have quick donning masks.

From 91.211:

(ii) At flight altitudes above flight level 350 unless one pilot at the controls of the airplane is wearing and using an oxygen mask that is secured and sealed and that either supplies oxygen at all times or automatically supplies oxygen whenever the cabin pressure altitude of the airplane exceeds 14,000 feet (MSL), except that the one pilot need not wear and use an oxygen mask while at or below flight level 410 if there are two pilots at the controls and each pilot has a quick-donning type of oxygen mask that can be placed on the face with one hand from the ready position within 5 seconds, supplying oxygen and properly secured and sealed.

For PT91 SP that requires O2 mask usage above FL350.

For PT91 crew if you have quick donning masks then no mask usage required until above FL410. If crew and one pilot leaves the flight deck above FL350 then other pilot must don mask.

For PT 135 see 135.89. For SP mask required above FL250. For crew with quick donning masks above FL250 to FL350 no mask required unless one pilot leaves duty station. Above FL350 one pilot of crew must be using mask.

Thanks Allen. I'm not above FL250 much, unlike you (g).


Best,

Dave

Thank you for that info. That's exciting.

Nice Jet!
Jason, I need to give you a ride in our Phenom....



(I'm seriously envious of your Pilatus though, and lust after a TBM, even if I can't afford the fuel)