LAS VEGAS (KLAS) — What were those mysterious lights Thursday over Las Vegas’ night sky?

Every so often, residents of the Las Vegas valley report such sightings and catch the sparkling illuminations on video. UFOs, perhaps? Military training? The airport? The speculation spreads.

Often, the bright glow can be traced to parachute flares and perhaps aviation training of some sort. Maybe Nellis Air Force Base, Creech Air Force Base or even Harry Reid International Airport is involved in some way.

A Nellis spokesperson Friday said no training was conducted over the valley the previous night. A Harry Reid airport spokesperson also was unaware of any activity that would produce strange illumination in the night sky. So how to explain the video, shared by viewer Bill — he asked not to use his last name — who lives in the southeast valley, near West Horizon Parkway and Stephanie Street.

Bill said he was in his backyard at about 9 p.m. when he noticed the lights in the sky northwest of his neighborhood and started to record. He thinks the lights were over the Strip and the old downtown area.

“I’ve seen tourist helicopters flying around the Strip before, but this was so much bigger and brighter,” he said. “At the end there, it looks like a plane might be coming in to land at the (Harry Reid International) airport.

“It was weird. The lights hung out for about five minutes or so, and then they were gone.”