The object was sighted by a private jet pilot, who claimed to air traffic controllers that some kind of flying craft got too close for comfort on Monday.
In a transmission that appeared on LiveATC.net, the operator of the Cessna Citation 525 CJ1 says: '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.'
A spokesman for the Federal Aviation Administration, Mike Fergus, told 9News that it is working to get some answers, and that if the pilot’s story is true, such an object can be extremely dangerous.
The object reportedly came dangerously close to the private jet, but it never appeared on radar
The mystery object was spotted by a pilot high above the city of Denver, Colorado, seen here