A flight recording apparently capturing a pilot reporting a UFO to air-traffic controllers has captured the public's imagination after it was shared on an aviation social-media channel.

The audio clip was published on a YouTube account called You Can See ATC, which uploads videos featuring pilots' accounts of emergencies or unusual situations during flights, such as equipment failures or fights on board. Most of the channel's viewers seem to be those working in the industry. However, a video published on the site two weeks ago has received more than 22,000 views so far, as a pilot describes seeing a 30-foot triangular object moving at speed from his cockpit window as he flew about 50 miles northwest of Frederick, Maryland, on December 20.

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