Technically, they are UFOs - unidentified flying objects - because no one knows what they are.
KDVR, a Fox-affiliated television station in Denver, ran a story about objects seen in the skies over that region.
A local man, who doesn't want to be identified, initially caught the images on tape. But the station set up its own camera, and filmed the same thing.
Reporter Heidi Hemmat thought the images might be drones from a nearby military installation.
But when she had an aviation expert evaluate the tape, he said they clearly weren't drones. The expert also said it wasn't a plane, helicopter or bugs (a popular suggestion from viewers who saw the tape).
Hemmat contacted the Federal Aviation Administration (FAA) and the North American Aerospace Defense Command (NORAD), which is based south of Denver.
Both agencies deny knowing anything about the flying objects.
Hundreds of people from around the world have flooded the station with calls and emails, but no one has come up an answer to the question: What is that in the sky?
Hemmat believes the flying objects are likely new experimental, military aircraft. But for now, the mystery continues.
You can judge for yourself by watching KDVR's broadcast, below:
- KDVR follow-up story: UFOs over Denver not bugs; images on video remain a mystery
This segment aired on November 23, 2012.