A video of a white object hurtling through the sky in Seoul has been uploaded to YouTube with claims that it's a UFO.
A plane passenger shot the footage through the window, and it was uploaded to YouTube on 7 April (too late for an April Fool's?)
The 'UFO' appears to be going at a similar pace to the plane, before speeding up and shooting out of the frame just as the person filming it tries to zoom in.
The YouTube user who uploaded it, crazybreakingnews, comments: "It looks a little bit strange and not really similar to the other videos. If it's really real and not a fake, it looks like a kind of military drone."
While some people believe it to be a real UFO, plenty of other users are extremely sceptical. One called Psued0Name said: "When stabilised, it is easy to see what is going on with the video.
"The edges of the UFO are not blurred like all of the other background objects, it seems like a separate effect from the background, and in fact you can see edge noise on the shape of the UFO indicating it's a fake.
"It doesn't even look right if you start to look at it hard, especially slowed down frame by frame."
It is not the first time a plane passenger thought he had filmed a UFO out of the window.
Last month, a traveller on a KLM flight believes he may have filmed a UFO through his window as the plane took off from Amsterdam Airport Schipol.
The video was filmed on an iPhone, and the passenger reportedly did not notice the object in the background until the next day.
Meanwhile, a total of six passenger planes reported seeing a UFO near the town of Gagarin in western Russia last October.
One, a pilot on a commercial flight from London to Moscow, claimed to see a 'burning object' followed by a trail of smoke going at high speed over the town, which was named after Yuri Gagarin, the first man in space.
Hundreds of miles away in Siberia, six red dots were reportedly seen an hour after the Gagarin 'sightings'.
What do you think it is in this case? See the footage below:
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