Meanwhile, Boeing has six unmanned airborne systems that vary widely in price, from about $100,000 each for its ScanEagle to a recent $29.9 million contract to supply two A160T Hummingbirds to the Marine Corps.

Boeing's efforts come at time when its defense business faces growing challenges. The loss of the Joint Strike Fighter contract to Lockheed Martin in 2001 locked the company out of new fighter work for decades to come. Meanwhile, Boeing has struggled in its competition for the Air Force's next generation aerial refueling tanker contract, while the company's massive Future Combat Systems program was scaled back last year.

Monday's test flight was the first time any craft other than the space shuttle orbiter has been transported on the exterior of the NASA plane.

"There's some apprehension when you do the first of anything," said Craig Brown, Phantom Ray program manager for Boeing.

On a bitterly cold afternoon, where the temperature hovered in the high teens, the cloudless blue sky provided ideal conditions for the test flight, said NASA project engineer Jill Brigham, who was at Lambert Monday. "There's a bit of excitement and a bit of relief," she said.