Tennis fans at the French Open were left scratching their heads after a plane appeared to fly backwards over a Grand Slam match.
The shadow of the plane could be seen travelling the wrong way across the court during the match between Serena Williams and Sloane Stephens on Monday.
A number of people took to Twitter looking for an explanation.
According to the Standard, one user, Zeb Goodman, asked: "Can someone explain to me why the plane shadow is going backwards?"
The aviation mystery, however, was soon solved: the jet was actually a model of a plane attached to an overhead camera.
The plane is an advertising tool at the Roland Garros court for sponsor Emirates, and when the camera moves backwards, it looks like the plane is flying backwards too.
According to the Mirror, another eagle-eyed spectator spotted the same thing at Andy Murray's match last week.
— th@und@d@wg ™ (@thaundadawg) May 25, 2015
Well, now we know.
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