Mysterious object nearly downed plane over Denver wrote:The Federal Aviation Administration is investigating a mysterious flying object that nearly caused a mid-air collision Monday evening over Denver, according to NBC affiliate KUSA.com.

The FAA says it has reviewed radar and audio recordings from the reported incident and hasn't found what it calls unidentified targets.

Investigators believe the object, whatever it is, could pose a serious safety hazard to planes.

For more on this mystery, visit KUSA.com

Radio transmissions from LiveATC.net confirm a nervous-sounding pilot reported a strange object at 5:17 p.m. Monday.

The pilot is 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 8,000 feet above sea level over Cherry Creek when the mystery object came close enough to make any pilot nervous.

"That's an issue because now we have something in controlled airspace that poses a danger," former NTSB Investigator and KUSA aviation analyst Greg Feith said.

Feith listened to the air traffic recordings and believes the object could be one of three things:

- A military or law enforcement drone.
- A remote controlled aircraft.
- A large bird.

"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.

Any one of those things can be catastrophic if it collides with an airplane.

On Wednesday, a local sheriff's office said it may have an explanation for the mysterious object.

The Adams County Sheriff's Office said deputies found a 14-foot solar bag Tuesday around noon. It's basically a weather balloon that looks like a long, black pool noodle. The FAA has not confirmed if the object is the solar bag.

Three years ago, a bird strike took down a commercial airliner that managed to land safely in the Hudson River. All the passengers survived.