Other local stations reported at least three dead including the pilot. The Los Angeles Times quoted emergency officials as saying that five people were killed.
The P51 Mustang called the "Galloping Ghost" was being flown by well-known stunt pilot and racing veteran Jimmy Leeward.
Mike Houghton, Reno Air Racing Association chief, said the National Transport Safety Board was investigating the crash that appeared to be caused by mechanical failure.
"There appears to have been a problem with the aircraft that caused it to go out of control," he said.
Organizers called the incident a "mass casualty situation" and MSNBC quoted rescue workers as saying that 75 were injured, 25 critically.
Witnesses said the plane slammed into the ground in front of grandstand filled with spectators at the Reno National Championship Air Races, sending debris and shrapnel flying into the crowd.
"There were lots of bodies with missing parts," Greg Schwab of Provo, Utah, told the Gazette. "I did not see a single person standing."
"It was the most sickening thing I've ever seen just watching the plane, there was no plane left," witness Greg Erny said.