A passenger aircraft above Scotland had a narrow miss with an unidentified flying object, a report by the UK Airprox Board has revealed.

The Airbus A320 was 4,000 feet above Glasgow when the incident occurred on a clear day at the beginning of December.

The report reveals that an alarmed pilot alerted traffic controllers to the presence of 'something' passing just 300-400 feet under his plane.

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The pilot logged the risk of collision with the object, which did not appear on radar, as 'high'.

A report by investigators was unable to establish what the object had been

The aircraft involved was approaching Glasgow airport on 2 December 2012 when the incident happened, according to the BBC.

The plane was making its approach over the Baillieston area of the city with landing lights on.

The non-flying pilot reported seeing an object "loom ahead" at a range of about 100m.

The cockpit transcript reveals the immediate aftermath of the alleged near-miss with the A320 pilots reporting the object was "quite large" and "blue and yellow".

The pilot sought confirmation of anything in the area and air traffic control confirmed they had nothing on radar. The controller said that he was not talking to anyone else in that area and that nothing had shown up on radar.

According to the BBC, once the aircraft had landed, the pilot told Glasgow Aerodrome Controller: "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 Airprox report concludes: "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."

Transcript of the conversation that took place between the aircraft and the controller:

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 err we've got nothing on err radar and we're n- not talking to any traffic either"

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A320: "Er not quite sure what it was but it definitely err quite large [1255:40] and it's blue and yellow"

EGPF: "OK that's understood err do you have a an estimate for the height"

A320: "Maybe err [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."