Complacency may have contributed to a mid-air collision between two vintage planes in a Battle of Britain Air Show, an investigation has found.
Two American Mustang fighter bombers collided during a display at Imperial War Museum Duxford in Cambridgeshire, on September 23 last year.
The tail of one made contact with the propeller of the other as they were joining formation with a larger Boeing B-17 aircraft during the display.
The pilots were able to land without further incident.
An inquiry by the Air Accidents Investigation Branch (AAIB) found the pilots had previously agreed that one would go to the right side of the B-17 and the other on its left side, but during the display they both tried to join on the right, causing a collision.
A "number of human factors were contributory to the accident," according to the investigation.
The most significant was that a walk-through of the display performed by the pilots did not include the part involving the B-17, and they were "predominantly focused" on the aerobatic section.
The AAIB concluded: "There appears to have been omissions, possibly resulting from a degree of complacency, during the briefings and subsequent walk-through."