An Ohio aviation crash expert on Monday said the fatal weekend crash at the Vectren Dayton Air Show may have been caused by the biplane’s left wings losing their lift, causing the plane to fall out of the sky.

However, a crash reconstruction expert and former Navy Blue Angels pilot from Austin, Texas, said flight control failure also could have caused the crash.

Both experts offered their opinions after reviewing video provided by the Dayton Daily News, but they cautioned that there isn’t enough information from the video alone to draw a firm conclusion about what caused the crash that claimed the lives of wing walker Jane Wicker and pilot Charlie Schwenker.

The performers’ 450 HP Stearman biplane was flying upside down Saturday with Wicker sitting on the higher wing when it hit the ground and burst into flames.

Wicker of Bristow, Va., was listed as the owner of the Boeing Stearman, manufactured in 1941. The Federal Aviation Administration had issued a certificate for the aircraft in 2010, which was valid through 2016.

The National Transportation Safety Board has launched an investigation that could take six months to a year. A preliminary report on the crash is expected later this week.

James B. Crawford, a reconstructionist with Introtech Crash Reconstruction in Grafton, near Cleveland, said the crash was likely caused by an “aerodynamic stall” of the left wings where the wing walker was positioned. Such a stall can occur when a wing does not generate enough lift to sustain the aircraft in controllable flight.

Crawford said it appears that the pilot entered the roll-over maneuver “at an airspeed that was too slow for a successful recovery, especially considering the extra weight and turbulence that the wing walker would exert on the (higher) left wing.”

Crawford is a retired Coast Guard captain who served as chief of the Avionics Branch of the Coast Guard’s Aeronautical Engineering Division. He has taught courses in motor vehicle, aircraft and watercraft crash reconstruction.

Even an aerobatic plane won’t generate lift while flying at 90 degrees, which is why the Stearman lost some altitude while in the process of rolling over, Crawford said. The roll-over maneuver must be completed quickly so that, once inverted, the wings can regain the ability to produce lift and keep the plane in the air.

Crawford said at 33 to 34 seconds into the video the rollover maneuver is almost complete and the pilot is adjusting the airplane’s nose upward so the wings can produce enough lift to stop the descent.

However, if the wings are angled up too much the airflow over the top side of the wings will become turbulent and all lift will be lost on those wings, creating an aerodynamic stall.

“At 34 to 35 into the video the left wing of the airplane appears to have stalled aerodynamically and it stopped producing lift on that side of the airplane, which caused the left wing to drop rapidly, and the ensuing roll caused the other wing to lose lift,” Crawford said. “Without lift the airplane could no longer fly, and it fell out of the sky.”

J.F. Joseph, a retired airline pilot and Marine Corps colonel who was a Blue Angels demonstration pilot from 1982-84, said flight control failure also could have been caused the crash.

“Whether it was a stall or a flight control failure, there is a pretty aggressive pitch up when the aircraft is inverted,” Joseph said, regarding the pilot’s actions to stop the roll rate just before the crash.

“You actually see the aileron on the low wing reflected up, which would raise the wing. It’s not long after that that you see the airplane essentially snap into that roll itself,” he said.

Joseph is the owner-operator of Austin-based Joseph Aviation Consulting and has nearly 30 years experience in aviation accident analysis and reconstruction.

He noted that when the plane enters the view from crowd left on the video, the left wings are slightly down instead of “wings level” as the pilot sets up for the maneuver. “It is quite obvious that the maneuver never does get quite to wings level,” Joseph said.

However, it doesn’t appear that Wicker obstructed or affected the flight controls while on the wing, he said.

“When the pilot gets to what is close to wings level, it looks like he begins to get somewhat aggressive with the pitch in trying to arrest the sink rate,” Joseph said.

The plane appears to enter the maneuver with enough energy not to stall, but something happens to cause its roll rate to rapidly increase. That could have been caused by a problem with the flight controls, he said.

“It could have been any number of things, but flight control failure is certainly something that the NTSB will look at closely,” Joseph said.