Glenn Maben, the director of flight operations for California-based Spectrum Aeronautical, and Nathan Forrest, vice director, were killed around 4 p.m. when the experimental nine-person plane crashed, said company president Austin Blue. Both men recently moved to Utah from Colorado to work on the project, Blue said.
''Glenn and Nathan were two of the finest gentlemen and pilots. Their loss is a great tragedy,'' Blue said by phone en route to Utah.
Witnesses told police the plane rolled to the right, clipped the ground with a wing and then cartwheeled until it came to rest several hundred yards from the runway.
"It would have been very difficult to survive this crash," said Spanish Fork police Lt. Carl Johnston.
The $3.65 million plane, called a Spectrum 33, boasted twin Williams engines and an all-composite frame. The lightweight nature of the frame, which made the plane almost half the weight of other aircraft in its class, was designed to increase fuel efficiency.
''This was the only one. We have to determine what went wrong,'' Blue said.
The plane took its first flight in January and was scheduled to be approved by the Federal Aviation Administration by 2008.
Spectrum built the plane in partnership with Utah-based Rocky Mountain Composites. Corporate officer Scott Wood said Tuesday after the crash, "We are deeply saddened by this loss and our thoughts and prayers are with the families of both the pilot and the co-pilot."
The composite construction of the plane, which includes the fuselage, wings, landing gear struts and all control surfaces, is made from an advanced material branded FibeX, produced by Rocky Mountain Composites.
"The result is a light simple, strong and durable airframe manufactured to precise tolerances," according to the Spectrum Web site.
Aviation industry officials as well as aviation press have been following the progress of the Spectrum 33 and have lauded the plane as revolutionary and innovative.
Maben and Forrest piloted the plane on June 30 when the six-year project was publicly unveiled. The event drew the attention of Gov. Jon M. Huntsman, who said through a spokesman that the technology was a monumental achievement for Utah, according to a report in the Provo Daily Herald.
But with investigators sifting through the wreckage less than three weeks later, the future of the project is less certain.
Spectrum employs about 80 people in Spanish Fork, south of Provo.
Blue said it was too early to know the impact on future production.
The Associated Press contributed to this report.