(CNN) -- The first sign there was a problem Friday with Virgin Galactic's SpaceShipTwo came at about 45,000 feet, just two minutes after it separated from the jet-powered aircraft that carried it aloft, officials said.
It wasn't something overt with SpaceShipTwo. It was what didn't happen.
"I knew when things weren't happening," said Stuart Witt, the chief executive of Mojave Air & Space Port, where SpaceShipTwo was launched and monitored. He didn't offer details.
"...If there was a huge explosion, I didn't see it."
Nothing seemed abnormal during the takeoff or flight prior to the spaceplane's failure, he said.
This much is known, according to Witt and others: One pilot is dead and another has been hospitalized with serious injuries.
The injured pilot was airlifted to Antelope Valley Hospital in Lancaster, California, authorities said.
There have been reports that the pilots managed to bail out, using parachutes. But neither Virgin Galactic or its partner conducting the test flight, Scaled Composites, have confirmed the accounts.
The two pilots worked for Scaled Composites, according to that company's president, Kevin Mickey. He declined to publicly identify the pilots or detail their experience.
"Space is hard, and today was a tough day. We are going to be supporting the investigation as we figure out what happened today, and we are going to get through it," Virgin Galactic CEO George Whitesides said.
"The future rests in may ways on hard, hard days like this."
Virgin Galactic has planned for years to sell trips in which SpaceShipTwo transports passengers about 62 miles above Earth -- the beginning of outer space -- and lets them experience a few minutes of weightlessness before returning to ground.
News of the crash of SpaceShipTwo came just after 10 a.m. local time (1 p.m. ET).
The incident occurred over the Mojave Desert shortly after SpaceShipTwo separated from WhiteKnightTwo, the vehicle designed to carry it aloft, the Federal Aviation Administration said in a statement.
Television footage from CNN affiliate KABC-TV in Los Angeles showed SpaceShipTwo in pieces in the Mojave Desert.
The National Transportation Safety Board is sending a "go team" to investigate the test flight failure, the agency said.
Virgin's chief, Richard Branson, confirmed the loss on Twitter: "Thoughts with all @virgingalactic & Scaled, thanks for all your messages of support. I'm flying to Mojave immediately to be with the team."
It's unclear what the failure of the spaceplane will mean for the program. Virgin Galactic planned to send paying customers on SpaceShipTwo as early as 2015.
With composite lightweight materials, "feathered" rudders capable of turning 90 degrees and a hybrid rocket engine, it is as safe as modern technology can make it. As designer and aviator Burt Rutan put it in 2008, "This vehicle is designed to go into the atmosphere in the worst case straight in or upside down and it'll correct."
Details of Friday's test flight plan were not immediately known. But in previous test flights, SpaceShipTwo has been loaded on the jet-powered WhiteKnightTwo, which can take the spaceplane to about 50,000 feet.
At that altitude, SpaceShipTwo would then fire its RocketMotorTwo -- a hybrid rocket engine powered by both solid and liquid fuel.
SpaceShipTwo would reach supersonic speeds on its way to its intended altitude of about 62 miles above the Earth. At that point, people onboard would get about five minutes of weightlessness before the bonds of earth retract with 6 G's of force.
The spaceplane would then glide back through the atmosphere to landing.
Friday's is the second incident in a week involving the commercial space industry.
On Tuesday, an unmanned Antares rocket exploded just after takeoff off the coast of Virginia. Controllers deliberately destroyed the craft after it became apparent there was a problem, a spokesman for Orbital Sciences Corporation said Thursday.
CNN's Brooke Baldwin, Rosalina Nieves, Sonya Hamasaki, Shelby Lin Erdman and Todd Leopold contributed to this report.
Here's video of a previous SpaceShipTwo test flight: