Self-described “aviation nut” Alan Meloy, from South Yorkshire, was taking photos of passing planes when he sighted Air Force One.
Mr Meloy captured the photo from his front door step as the presidential aircraft soared over the suburb of Chapeltown.
Air Force One, the name given to two VC-25 planes used by Mr Trump, was flying under a false call sign to keep the trip to Iraq a secret.
Mr Trump and First Lady Melania had left Washington DC in the middle of the night without fanfare, so when Mr Meloy posted his photograph on the sharing site Flickr his claim was met with some scepticism.
But other enthusiasts recognised the plane, and when cross-referencing the image with tracking data, deduced the president was likely heading to the Middle East.
With the news being so widely discussed online thanks to the photo, a ban on reporting the trip, agreed with the White House press corps, was lifted.
Mr Meloy has found himself the centre of attention on both sides of the Atlantic.
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He told the Guardian: “It’s one of those weird moments where you’re right place and right time.
“Boxing Day dawns clear and bright, the next thing there’s an interesting airplane.”