A woman was left in “total confusion” and “creeped out” after she saw a strange black shape floating in the skies.
Aiyana, who asked that her second name be withheld, recorded the surreal footage from the roof of her home in Chicago, Illinois.
The video shows a long black wishbone shape hanging in the air, with both its wings ending in some sort of sphere.
She said: “I literally have no idea what it was. There is nothing comparable.
“It was a ball of some sort with two long strings or belts hanging from it. The strings had knobs in the middle and bottom.”
Aiyana and her son said neither of them “had any idea what we were seeing”. She said she stayed watching it until it disappeared from view.
“It seemed to just float slowly south east without any other major movement,” she said. “It covered a few miles in about 20 minutes.”
“I felt total confusion and a bit creeped out,” she added.
Hoping to find answers, a friend shared Aiyana’s footage with UFO watchers online but no one was able to explain how an object could float so calmly above the famously “windy city”.
One person wrote: “I’ve never seen a balloon just hang still in the open air like that. It should bob, even if just a little. There must be absolutely zero wind there.”
Another person described the sighting as “bizarre”, adding: “I have no explanation. It looks like something hanging from a helicopter, except there is no helicopter.
“The shape is too weird for it being a balloon, and I think I can also exclude it being an antenna on top of a building in cloud cover – for this, it is way too clearly defined.
“I have no idea!”
A third said: “A balloon usually has some movement. I live in Chicago. Even on a still, calm day, Chicago and the surrounding areas have wind of some sort and would move something in the air.”
The unexplained sighting is just one of several in the US in recent weeks.
Another video, captured in Baltimore, Maryland, attracted a deluge of comments revealing identical sightings in numerous states.
In September, a man spotted what appeared to be glowing orange UFOs “flying in formation” when returning home.
When he posted the footage online, social media users recalled similar sightings in Washington DC, Las Vegas, St Louis and Detroit.
Meanwhile in the UK, a woman was left baffled after capturing an image of a possible UFO hovering in the evening sky over St Helens, Merseyside while taking a friend on a late-night drive.
She later told the Liverpool Echo : “I couldn’t see any lights around it or anything, you can just see the blue thing in the sky. I was just taking a picture of the Moon while we were out because I thought it looked nice.”
She added: “We were just like oh, my god, it does look like a UFO. It does look like a ship, it doesn’t look like a plane or a light, it looks like a UFO.
“I sort of believe in them. I’m not a strong believer but I do believe there are aliens out there and stuff like that.
“It’s interesting. You can see it but it was strange. I believe more now I can see it.”