High altitude endorsement is nothing more than learning the pressurization systems, emergency procedures, and studying hypoxia stuff. I have not gone to UPT yet, but I imagine you learn those sort of things for each a/c you fly. I have my high altitude endorsement, but after getting it I sure didnt feel like I knew what I did to get it. It was just like my high performance endorsement, basically go fly and work with the system and voila there you have it. VERY EASY! I wish all my checkrides were that easy!! :cool: Question: if the IP wont/cant sign you off (i.e. not an FAA CFI), then how can you legally go solo in the a/c?? To solo in any a/c in private pilot training, you had to have all your normal sign offs that that a/c entailed. Wouldnt you need the same for the T-6 or T-37?