An investigation has found that complacency could have contributed to a mid-air collision between two vintage planes at an airshow in Cambridgeshire.
It happened at the Battle of Britain Air Show in Duxford last September, when the tail of one Mustang fighter made contact with the propellor of another as they were joining formation with a larger Boeing B-17 aircraft during the display.
The pilots were able to land unharmed.
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 said: "There appears to have been omissions, possibly resulting from a degree of complacency, during the briefings and subsequent walk-through."