Dayton International Airport spokeswoman Linda Hughes and Ohio State Highway Patrol Lt. Anne Ralston confirmed the deaths to The Associated Press.
The crash happened at around 12:45 pm (local time) at the Vectren Air Show near Dayton. No spectators were injured. The show has been cancelled for the remainder of the day. The names of those killed weren't released immediately, but a video posted on WHIO-TV showing the flight and crash identified the performer as wing walker Jane Wicker. A schedule posted on the event's website also had Wicker scheduled to perform.
"All of a sudden I heard screaming and looked up and there was a fireball," spectator Stan Thayer of Wilmington, Ohio, told WHIO.
Another spectator, Shawn Warwick of New Knoxville, told the Dayton Daily News that he was watching the flight through binoculars.
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"I noticed it was upside-down really close to the ground. She was sitting on the bottom of the plane," he said. "I saw it just go right into the ground and explode."
She told WDTN-TV in an interview this week that her signature move was hanging underneath the plane's wing by her feet and sitting on the bottom of the airplane while it's upside-down.
"I'm never nervous or scared because I know if I do everything as I usually do, everything's going to be just fine," she told the station.
"What you see us do out there is after an enormous amount of practice and fine tuning, not to mention the airplane goes through microscopic care. It is a managed risk and that is what keeps us alive," she wrote.
In 2007, veteran stunt pilot Jim LeRoy was killed at the Dayton show when his biplane crashed and burned.