The pilot of the Beech Bonanza 3,000 feet above us had never seen anything like it: a 747 with a bizarrely swollen engine buzzing the Mojave Desert at 300 feet. The control tower eased his fearsit's just GE's Flying Testbedbut aboard the jumbo jet I was a bit nervous. For 10 minutes we got no higher than 400 feet, at nearly 300 mph, powered by one engine.