SPANISH FORK — An experimental plane crashed at the city airport Tuesday after takeoff, killing two people who worked for a company building the lightweight aircraft in Utah County.

"It was a test flight. We've had many test flights. I don't know what went wrong with this one," said Austin Blue, president of Spectrum Aeronautical LLC, based in Cardiff by the Sea, Calif.

The victims were Glenn Maben, Spectrum's director of flight operations, and Nathan Forrest, vice director, Blue said. They had recently moved to Utah from Colorado.

The wreckage was strewn northwest of the runway at Spanish Fork City Airport, which was closed after the crash was reported about 4 p.m.

"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.

The plane was a Spectrum 33, a twin-engine jet made of carbon fibers, he said.

"This was the only one. We have to determine what went wrong," Blue said.

Spectrum employs about 80 people in Spanish Fork. Blue said it was too early to know the impact on future production.

Rocky Mountain Composites, Inc. of Spanish Fork and Spectrum Aeronautical in June celebrated the first public flight of the plane.

The plane's composite carbon-fiber skin, produced by RMC, is what makes it different from other similar planes.

Most aircraft bodies are made up of various metals, but the body of the Spectrum 33, with a price tag of $3.65 million, is one piece of carbon-composite material, RMC's proprietary FibeX.

Comparable jets weigh around 13,000 pounds, while the Spectrum is about 7,000 pounds. With the cost of fuel, the lightweight spectrum will be more appealing to pilots than similar planes.

Contributing: Associated Press, Deseret Morning News staff