Two RAF jets were involved in a near miss with a glider which crossed their approach path as it took part in a competition, a report has revealed.
The glider was approximately 925m away from the Tornados as the jets prepared to land at RAF Marham in Norfolk last August.
The UK Airprox Board said RAF Marham's air traffic controllers were "shaken".
Investigators said one of the reasons for the incident was the "late sighting" by the Tornado crew.
There was also "probable non-sighting" by the Ventus glider pilot.
The board heard how organisers set a route just half a mile from the Marham zone on a difficult gliding day and had "forgotten" to tell Norwich Air Traffic Control or "thought to tell" Marham.
The board recommended the British Gliding Association now advises competition organisers how to detail plans in official alert notices for the authorities.
Marham's air traffic controllers spotted about six gliders as the Tornados - which were running low on fuel - were waiting to land, but that radio attempts to contact them failed.
Only one glider had its safety transponder turned on, which meant plane pilots must instead "see-and-avoid" which, the report said, is "notoriously difficult" as gliders can be difficult to spot.
The board also supported a recommendation made by RAF Marham's own inquiry that a collision avoidance receiver - currently on trial in some military control towers - is installed.