If the truth about UFOs really is out there, don't bother telling the Australian government.

Department of Defence documents previously marked "SECRET" show the Royal Australian Air Force moved to stop investigating UFO reports in the 1990s because the majority weren't visitors from outer space and only about 3 per cent of sightings could not be explained.

The policy statements and correspondence, released through freedom of information laws, outline a new policy for RAAF personnel to refer reports of sightings to civilian UFO groups.

Between 1960 and 1973, about 815 UFO sightings were reported to Australian authorities.