Paxing in an 8 seater twin turboprop would be not quite true, but I certainly couldn't fly it. I sat with my back to the cockpit, all the better to be snarled at by the Aussie pilot who didn't care for me much, or at all. We were sort of on business, going round South America. We were flying from Londrina (pretty much at sea level) to Potosi airfield (very much not at sea level - the town is at about 13,000 feet and the richer you are the lower you live as oxygen is precious there) which was a dirt strip at about 13,500 feet. This is Potosi, Bolivia, SLPO, by the way, not the Mexican airport. Flying in the Andes is an astonishing privileged experience, with these beautiful snow-capped mountains in a cruel razor sharp double ridge down the spine of South America. As we came towards the strip, the pilot shoved the thick manual in my hands over his shoulder and asked me to see how much power we would have for take off. I looked for the graph, and, having inspected it, truthfully told him I didn't know. He swore and grabbed the book off me. He lowered the undercarriage. He went back to the book and swore again, louder and worse. He saw why I couldn't work out the power - the graph ended at 7,000 feet altitude. We bumped down, and he parked up. As the engines died, there was a hiss of air round the doors. It was cabin air ESCAPING. As you stepped out of the plane, there was no sensation of wind as there was hardly any air. I trotted down the steps to the front of the plane and found myself gasping for breath. I felt very odd and slept little that night with a pounding heart (another altitude effect) and the next day we returned to the plane. From memory, the strip was about 6,000 feet. It's listed as 9,000 now. The pilot made us push the plane to the very end of the runway. By which I mean the tail was hanging over a cliff over a dizzying drop with the main landing gear about a foot from the edge. Unusually, as we were reasonably well acquainted with the aircraft he insisted on doing a preflight safety briefing. I can honestly say that I have never had a briefing before or since that started with the words, "Now listen you sh1ts, if I get killed... " He went on to identify the throttles, fire extinguishers, radios, beacons and emergency rations to an increasingly silent cabin. We still had no idea how much power the engines would make but it seemed obvious that if we didn't get airborne off the end it would be a quick death several thousand feet below. Ahead of us was a beautiful snow covered 21,000 foot mountain. We all strapped in as tightly as admittedly sweaty palms allowed. As I was facing backwards over the wing all I could see was fresh air. He started the props, and put on power with the plane held on the brakes before releasing them. We moved forward at the speed of a moped. We didn't seem to be accelerating at all. We trundled down the runway and suddenly he pulled back on the column with another oath. "Jesus Christ, there's a man on the runway!" We flashed over and presumably mightily startled a man with his donkey who had been quietly filling a hole in the strip, but it meant we had too little power to climb properly. We lumbered soggily ahead, the beautiful mountain came ever closer, and the pine trees on the lower slopes started to become visible as individual trees rather than a green mass. Nobody said a word. The mountain gradually enlarged over what felt like about an hour but was probably less than a minute until it threatened to fill the windscreen, when suddenly, the port wing dropped, and we seemed to slide down the side of the mountain into a slightly lower valley and as we fell we gained speed. After another very long pause the pilot straightened the wings and we slowly climbed to FL240. I understood that day what proper pilots did.