California, Florida and Washington top the rankings for most UFO sightings.

There was a rise in the number of North Americans who looked up into the sky in 2019 and found something that didn’t look like a bird or a plane.

The National UFO Reporting Center, which tracks calls and messages from people around the U.S. and Canada about strange sightings in the sky, reported that it received 5,971 sightings in 2019 -- a jump from 3,395 in 2018.

Peter Davenport, who runs the independent organization that's based in Davenport, Washington, said he couldn’t explain why more people called about seeing flashing white lights, fireballs, disc-shaped objects or other oddities in 2019.

"One of the mysteries of ufology is there is a fluctuation in the number of reports over the years," he told ABC News in a phone interview. "Some years it’s been low, but it’s gotten higher recently."