I wanted to join the mile high club so I asked my wife to meet me in the rear lavatory because it was the largest. After meeting her and locking the door it was the old ” in out” for about 15 minutes. I then got out and while walking back to my seat I almost blacked out. I think because of the thinner air. I don’t know what the inside was pressurized to but I’m guessing 11 to 12 thousand feet. Maybe some jet pilots could answer that. But I enjoyed joining the mile high club!