It was the bizarre sight that had pilots and air traffic controllers stumped.
Flying high above the ground over Crater Lake in Oregon, an unregistered aircraft was causing havoc as baffled pilots radioed in reports of an unidentified object flying outside registered flight plans.
On the ground, it was a similar situation, with radars alerting air traffic controllers to a mystery object in the air.
Now audio obtained by blog The Drive has revealed an exchange between officials as they struggled to figure out the incident last October.
"You know that target south of the boundary there? The 0027 code moving very fast at 37,000?" a radar operator can be heard saying.
"Oh, look at that thing,” replies a centre controller. “Huh, um and you don’t have anything on him?"
With the operator replying he didn’t, the Sun reports sightings of the object continued for another 30 minutes, and saw another United Airlines flight calling in reports of a ‘large white plane’.
Officials took the sightings seriously, with F-15 fighter jets later taking off from Portland International Airport in a bid to investigate and intercept the object.
However their search was futile as the flying object has mysteriously vanished.
"The fighter scrambled, they went out looking around a little bit but we, you know, we lost anybody having sight of the aircraft,” the Sun reports a FAA Seattle Center Official saying.
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