A weird video appears to show a shiny object zipping through the skies adjacent to a passenger plane that is taking off from the city of Philadelphia in Pennsylvania.
In the clip, recorded from inside the plane, the silver shape zips along at some speed in a horizontal path.
"What is that?" says a woman in the background.
The weird footage was recorded by Mariah Lyn and has sparked debate after being uploaded to the paranormal Youtube channel The Hidden Underbelly 2.0 where it was described as a "fast-moving UFO ".
Narrating the video, the YouTuber says: "To me, this object seemed to be traveling pretty fast.
"And it looked metallic and dome-shaped, almost like your classic flying saucer."
He says it was filmed shortly after take-off at around 11:20am on August 20.
"This thing doesn't look like a drone, it certainly doesn't look like a plane, I mean there's no wings, there's nothing," the conspiracy theorist says.
Many viewers agreed that the object was alien in origin and said it was an "authentic" catch.
"I've seen those many times, they can often be found hanging around clouds," commented one.
A second said: "It’s almost redundant to say amazing footage in 2020 but brilliant footage."
"IMO [in my opnion] this is 100% authentic footage," said another viewer, adding that the object appears to be "moving much faster than commercial air traffic".
This comes after planetary defences spotted a "UFO" hurtling towards Earth – but it turned out to be NASA relic.
And a "triangular craft" alleged to belong to the US military was recorded hovering over Indiana.
Conspiracy theorists claim it is proof that the "secret spy plane" really does exist.