A sensational two-minute clip documents the meeting off the East Coast three years ago.
The clip features crew of a F/A 18 jet watching the mystery craft below from 25,000 feet.
“What the f*** is that thing?” the pilot proclaims, laughing in amazement.
The jet’s weapons systems officer is heard saying: “Oh my gosh dude.”
At breakneck speed the UFO heads underneath the American fighter.
The video, released by the Stars Academy of Arts and Science, is now the third featuring unexplained incidents involving US military planes and UFO.
And it has led a former key official in the Bush and Clinton administrations to urge the US government to take action.
Writing in the Washington Post, Christopher Mellon said: “Is it possible that America has been technologically leap-frogged by Russia or China?
“Or, as many people wondered after the videos were first published by the New York Times in December, might they be evidence of some alien civilisation?
“Unfortunately, we have no idea, because we aren’t even seeking answers.”
Footage emerged last year of a sighting involving jets from the battleship USS Nimitz in 2004 off the San Diego coast.
Both the Nimitz and F/18 strange encounters were believed to have been investigated as part of the Pentagon’s top-secret Advanced Aerospace Threat Identification Program (AATIP).
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“Might they be evidence of some alien civilisation? Unfortunately, we have no idea, because we aren’t even seeking answers.”
Ex Bush official Christopher Mellon
This groundbreaking programme, had a budget of £16.5million allocated to it annually by the Department of Defence.
Military intelligence officer Luis Elizondo, who ran AATIP, recently made astonishing claims about how investigators believed they had been to understand how the UFOs fly.
Working with expert scientists, they believe the craft can effectively create their own time-space bubble, which allows them to fly at such incredible speeds.
While the US government said AATIP was closed in 2012, Elizondo claimed he worked on the highly-sensitive project until October last year until he resigned over “excessive secrecy and internal opposition”.
Mr Mellon said that the bizarre reports from US military staff who have encountered the craft must be investigated further.
“These mysterious aircraft easily sped away from and outmanoeuvered America’s front-line fighters without a discernible means of propulsion,” he wrote.
“From my work with To the Stars Academy, which seeks to raise private funds to investigate incidents like the 2004 Nimitz encounter, I know they continue to occur, because we are being approached by military personnel who are concerned about national security and frustrated by how the Defense Department is handling such reports.
“If the origin of these aircraft is a mystery, so is the paralysis of the US government in the face of such evidence.”