Red Arrows pilot Jon Egging was killed because his aircraft may have hit a bird, say investigators.
A "catastrophic bird strike" could have extinguished the flame in the Hawk T1's jet engine, cutting power, a senior RAF source told the Daily Mail.
The news comes as investigators revealed they had found bird remains at the site of the crash.
The 33-year-old pilot had been taking part in a display at Bournemouth Air Festival when the jet went out of control and crashed into the bank of a river – watched by his wife Dr Emma Egging, 32.
Egging managed to steer the plane away from houses in the village of Throop before crashing. Egging's body was found face down in the River Stour, with his ejector seat, helmet and parachute nearby.
Experts have said that Egging might have been unable to eject himself from the jet because of the huge G-forces he was battling against.
Egging's grandmother Doris Egging, 88, from Southam, Warwickshire, told the Daily Mail: "Jon was a hero but he probably didn’t eject because he was unable to after being knocked out.
"I spoke to my son, Jon’s father Philip, and he sounded ill. He couldn’t take it in.
"I’m told they were coming back at quite a height and this may have sent Jon’s plane out of control. Philip was told Jon was higher than he should have been when he banked.
"I would very much believe he would sacrifice his own life to save others, that’s the way he was."
Egging and his wife Emma married last June in Morcott, Rutland. His father was a BA pilot.
"Flying with the Red Arrows was his dream. He was so proud, as we all were of him," added his grandmother.