A Chinook and Spitfire had a near miss after a practice display ahead of an air show.
The helicopter was cleared to land on a runway at RAF Cosford, Shropshire on 9 June but had to move after the co-pilot saw the Spitfire coming in.
The Spitfire pilot said he only saw the aircraft as he approached the runway.
A UK Airprox Board report said the aircraft came within 40ft (12m) of each other.
It happened a day before the annual RAF Cosford Air Show.
A report by the board, which investigates near-misses by aircraft, said the helicopter had been hovering at 25ft (7m) following its practice, but had to move as the Spitfire came to land.
Transcripts show the plane's pilot was given permission to land, but had been told there was a helicopter on the runway.
In his statement, the pilot explained he took the clearance to mean it was "my runway".
The report added the Cosford Aerodrome Controller assessed the level of risk of collision as "very high".
It said the controller had expected the Spitfire to follow military guidance not to approach below 500ft (152m).
But the pilot believed the clearance included for a "display" arrival at about 30ft (9m), as he had done for 15 years previously at Cosford.
The board said no supporting documents provided by air show organisers included information about the minimum height, which was a "contributory factor" in the incident.
In the report, Joint Helicopter Command said "swift and calm reaction" by the Chinook's crew prevented the "potentially disastrous" collision.
RAF Cosford Air Show said it would not be commenting further.