Footage showing a strange object streaking across the sky beneath a jet plane has emerged, prompting questions about what the other aircraft could be.

Filmed a few years ago but released this week, the video - which was uploaded to YouTube - shows the view outside the left side of a carrier aircraft with the wing in sight.

Posted by Finding UFO, a group whose aim is to spot unidentified flying objects across Australia, the footage shows a small white disc zooming across the sky in the blink of an eye through the airspace above Canberra.

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Footage has emerged showing a strange object streaking across the sky above Canberra

Entering from the left hand side of the screen the object appears to be travelling at great speed as it streaks past along the clouds.

It then seems to transit beneath the plane and out of sight

'An unidentified flying object was caught on camera from an airplane near Canberra, Australia on April 04, 2012,' the video's description reads.

Appearing on the left hand side of the plane the object appears to be travelling at great speed

It then disappears under the plane and out of sight, and does not look to be another plane or helicopter

'It was filmed by a passenger.

'The UFO was flying very fast below the Aircraft. It doesn't look like a normal plane or helicopter but it looks like a flying saucer.'

It is unclear why the passenger on the plane was filming out the aircraft's window, but commenters on the video have backed the legitimacy of the footage.

Finding UFO have uploaded many similar videos over the past few years, purporting to show UFOs in various destinations around the world including Melbourne, Hong Kong, Hamburg, Brazil, and Chile.