One passenger gazed out of the window to find an unusual sight at 35,000ft: another aircraft flying past.

William Cherry was on an Aer Lingus flight from Dublin to Lisbon when he noticed the plane and its jetstream out of the window, and swiftly captured a video.

The footage, which has had more than 3,000 views on Twitter, shows another jet flying past the window – although it’s unclear how close it actually is.

“What constitutes ‘a near miss’?”, said Cherry on Twitter.

“This happened on my flight from Dublin to Lisbon yesterday!! Hasn’t helped my fear of flying!”

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He told Dublin Live that he was happy to reach his destination – and that no other passengers onboard had noticed the neighbouring jet.

The UK’s aviation watchdog has strict rules on how close aircraft can be. Below 29,000ft, the distance is usually three miles horizontally or 1,000ft vertically. The video appears to show the plane above 29,000ft.

“Once an aircraft is in an airway the horizontal separation normally increases to five miles,” says the Civil Aviation Authority.