Witnesses say they heard sputtering and a pop before a new model of a Wright Brothers biplane crashed in rural western Ohio, killing the two volunteer pilots.
The Dayton Daily News reports one man living nearby said the plane was sputtering late Saturday morning. Another heard the engine backfire and then a pop.
The plane went down during flight testing in an area of cornfields about 3 miles from Springfield Beckley Municipal Airport, where it had taken off earlier.
The 73-year-old and 64-year-old pilots who died were experienced in flying the biplane. It was built by a company that uses them to promote nearby Dayton as the birthplace of aviation.
A Federal Aviation Administration spokesman told the Daily News a finding on what caused the crash could take eight months.
Information from: Dayton Daily News, http://www.daytondailynews.com