Denver ColoradoThe Federal Aviation Administration has launched an investigation after a mysterious object in the skies over Denver almost caused a mid-air collision on Monday.

Investigators are reporting that the mysterious object did not show up on any known radar.

The FAA now acknowledges that the object could pose a serious safety hazard to planes in the area.

Radio transmissions from confirm that a nervous-sounding pilot did indeed report a strange object at 5:17 p.m. local time on Monday evening.

The pilot can be heard telling air traffic control:

“A remote controlled aircraft, or what? Something just went by the other way … About 20 to 30 seconds ago. It was like a large remote-controlled aircraft.”

The corporate jet, a Cessna Citation 525 CJ1, was flying at approximately 8,000 feet above sea level when the UFO got close enough to make the pilot nervous.

“That’s an issue because now we have something in controlled airspace that poses a danger,” said former NTSB investigator Greg Feith.

Feith listened to the transmissions from the pilot and thinks the object could possibly be a military or law enforcement drone, a remote controlled aircraft, or a large bird.  Then again, it could be something else entirely.

“Was this an unmanned vehicle that was part of some sort of law enforcement operation? Was this somebody that had flown a large model aircraft inadvertently into the airspace? Or was it just [a bird that] caught the pilot’s eye so he believed it was an aircraft but could have been a very large wing span bird,” Feith said.

Check out more in the video below.