ONE OF THESE DAYS, GEORGE Heaven will boldly fly into the wild blue yonder for two minutes or so and, after traveling 1½ to 2 miles at about 100 feet, glide gently back to earth.

Unless the rubber band snaps. Heaven, 44, has spent 3½ years perfecting his plane, Rubber Bandit. It's 33 feet long, weighs 310 pounds and is powered by a huge rubber band made of 3½ miles of intertwined rubber-band thread. If Heaven is correct—a darn big if—the giant band will unwind in the fuselage, turn the propeller at 350 rpm and make him the first human borne aloft in a rubber-powered aircraft. If he's wrong, headline writers may need look no further than the word "SPLAT!"

For Heaven, a former stunt pilot and skywriter who lives in Woodland Hills, Calif., with his girlfriend, Donna Eichinger, the concept of rubber-powered flight first took wing when a radio show asked for help building a giant slingshot as a publicity stunt. When that didn't pan out and the station abandoned the idea, Heaven, a freelance aeronautical engineer, stuck with it—and evolved the idea of Rubber Bandit. "I'd already spent nine months on the project," says Heaven. "I said, 'I'm going to finish it.' " The venture has cost $185,000, acquired through donations and fund-raising schemes, much of it for materials—mostly ultralight plastic compound—and hangar space at Van Nuys Airport.

With Rubber Bandit almost ready for its maiden flight there's just one more question for George Heaven: Does his technology have any, er, practical application? "Not unless," he says, "the world runs out of fuel."