A passenger plane in Glasgow has reported a near-miss with a UFO.
A report by the UK Airprox Board revealed that a startled pilot alerted traffic controllers to the presence of 'something' passing just 400 feet under his plane.
But neither the local air traffic team at the time, or investigators since, have been able to establish what it was.
The Airbus A320 involved was approaching Glasgow Airport on 2 December 2012 when the incident occurred, according to the BBC.
The plane was flying about 4,000ft above the city, with its landing lights on and on a clear day.
The crew of the plane said that the UFO was moving quickly, but was yellow or silver and "bigger than a balloon".
But the air traffic team said that nothing had appeared on radar, and they had no idea what the object was. A radar at Prestwick did register an "unidentified track history" 1.3 nautical miles east of the plane about 28 seconds earleir, but that hasn't given many clues about the flying object's identity.
The pilot said once he had safely landed:
"We seemed to only miss it by a couple of hundred feet, it went directly beneath us. Wherever we were when we called it in it was within about 10 seconds. Couldn't tell what direction it was going but it went right underneath us."
The report concluded:
"Investigation of the available surveillance sources was unable to trace any activity matching that described by the A320 pilot. Additionally there was no other information to indicate the presence or otherwise of activity in the area."
The transcript for the incident reads:
The Airprox report included a transcript of the conversation that took place between the aircraft and the controller at 12:55:
A320: "Glasgow Approach [A320 C/S]"
EGPF: "[A320 C/S] pass your message"
A320: "Er yeah we just had something pass underneath us quite close [1255:30] and nothing on TCAS have you got anything on in our area"
EGPF: "Er negative er we've got nothing on er radar and we're n- not talking to any traffic either"
A320: "Er not quite sure what it was but it definitely er quite large [1255:40] and it's blue and yellow"
EGPF: "OK that's understood er do you have a an estimate for the height"
A320: "Maybe er [1255:50] yeah we were probably about erm four hundred to five hundred feet above it so it's probably about three and a half thousand feet."
The report said the Airprox board did not think the UFO was a helicopter, fixed wing plane or a hot air balloon. They added it was possible the object was a glider, but said that since thermal activity was low on such a cold day, that was unlikely too.
The board concluded it did not have enough information to determine a cause or risk.