Could it be a UFO? Some type of weather balloon? Many shared images and videos on social media, and the speculation was rampant.
The white orbs first seemed to make news headlines on Tuesday in Ohio. A bright, white dot was seen in the sky over Dayton and surrounding areas.
On Thursday, two strange objects appeared over Kansas City. A YouTube video showed the bright orbs against the blue sky, floating above an airplane.
Even Kansas City's National Weather Service said it was stumped.
"We honestly have no explanation for the floating objects over Kansas City," the office wrote on Twitter. It then followed up with a photo showing the two tiny, white spheres in the sky.
Some speculated the mystery objects in the sky could be balloons as part of Google's Project Loon, which partners with mobile networks to expand LTE coverage in places with limited connectivity.
But Scott Coriell, who heads global communications at Loon, said in an email that it wasn't them.
Instead, the floating orbs turned out to be balloons that belonged to Defense Advanced Research Projects Agency (DARPA).
The agency's chief of communications confirmed in an email that they were part of DARPA's Adaptable Lighter Than Air Program.
On June 18, DARPA launched three balloons from Cumberland, Maryland in a flight test for the project. DARPA also tweeted about the launch, stating that over the next few days, "ALTA will demonstrate capability for wind-borne navigation of a lighter-than-air vehicle over extended ranges."
According to the project's website, the balloons can fly at altitudes of more than 75,000 feet.
While the balloons ended up not being evidence of an alien invasion, the Pentagon did reportedly admit in a recent New York Post report that it still investigates claimed sightings of UFOs.
This story was reported from Los Angeles.