A witness told the National Transportation Safety Board a plane was doing aerobatics moments before it crashed near Fairmont last week.
Pilot Randy Harris, 55 of Owasso and his passenger, 1st Lt. Dale Shillington, 25 from Vance Air Force Base, died in the crash on Thursday, July 21, 2016.
In its Preliminary Report on the crash, the NTSB says the Skybolt 300 biplane had taken off from Enid Woodring airport at about 6:30 p.m.
Lt. Shillington's wife told investigators the flight was a "last minute" event, and that she was supposed to meet the plane at Vance Air Force Base about 15 minutes after the plane took off.
The plane crashed at about 6:40 p.m.
A witness who was about a half a mile from the crash location told the NTSB he saw the airplane fly over his house at high altitude and perform a barrel roll about 30 seconds before the incident.
As the airplane continued to head south he saw it begin to climb straight up, according to the NTSB. The nose of the airplane then came down to the horizon and the airplane started "tumbling" in the same way he'd see other aerobatic planes do, he told the NTSB.
According to the NTSB, as the airplane got a third of the way through the tumble it rolled onto its back and entered an inverted flat spin, the witness said. He saw it go behind some trees but did not see it hit the ground.
The witness said he heard the engine running the whole time, until he heard the sound of the airplane hitting the ground, according to the NTSB.
Harris was an airshow pilot and was scheduled to perform at the Vance Air Force Base Airshow and Open House on Saturday, July 23, 2016.
According to his web site he retired from American Airlines in 2011 and had also been a flight test engineer for McDonnell Douglas and was general manager of Aircraft Specialties Services in Tulsa.
His funeral service is set for Saturday, July 30, 2016 at the Tulsa Air & Space Museum.
Lt. Shillington was a T-38 instructor pilot based at Vance AFB.
The Preliminary Report is the first of three reports the NTSB issues on a fatal crash. The Factual Report is usually released several months after the incident, followed by the Probable Cause which can take years to complete.