(FORTUNE Magazine) – Probably the most fun plane I have is a Russian fighter jet. It's called an L-39. It has a Czech air frame, a Ukrainian engine, Russian avionics. It's what they used to train their fighter pilots on, so it's incredibly acrobatic. But your butt hurts if you fly in it for more than an hour. The seats are really hard.

You can do eight Gs in that plane. You pretty much need a G-suit, or you could black out. I might go up to five, but that's the most. Five Gs means that's five times your body weight. It's pretty hard to move. You feel very heavy. Your cheeks are being sucked down. If you maintain five Gs for too long, it's very hard to concentrate. You start seeing red dots.

Probably the most fun flight I did was with another L-39 in Nevada. It's kind of open airspace, so we did a tail chase, where we basically followed another plane through the mountains at very low altitude. Literally, it was just like in Top Gun. You're no more than a couple of hundred feet above the ground, following the contour of the mountains. We came up to a mountain, did a vertical climb up the side of it, inverted. Turned upside down. Yeah, that was fun. It's like a roller coaster. Only you go much farther up and down.