A bizarre UFO that "defied physics" outmanoeuvred several F-18 pilots during a terrifying encounter, a former senior US national security chief who spent time at the mysterious Area 51 military base has sensationally claimed.

US Navy personnel aboard the USS Nimitz even filmed the UFO during the encounter that lasted several hours, according to Chris Mellon.

Mr Mellon served for almost 20 years in the US federal government in a series of national security positions roles under presidents Bill Clinton and George W Bush.

The ex-national security chief, who had high-level clearance, was on a committee with oversight of all Department of Defence (DoD) special access programmes and spent a decade on the Senate Intelligence Committee, is one of a number of former senior government insiders who have gone on record about UFOs after joining truth-seeking organisation To The Stars Academy, set up by former Blink 182 frontman Tom DeLonge.

Mr Mellon, who also worked on classified projects at Area 51 in Nevada, detailed the astonishing incident that reportedly happened off the coast of San Diego in broad daylight.

He said the Mimitz, a five billion dollar warship with a crew of thousands, was operating there, escorted by the USS Princeton, an Aegis class cruiser.

Mr Mellon said: "Imagine these ships engaging in a routine training exercise when an unidentified aircraft with a small radar cross section appears on the radar heading directly towards the battlegroup.

But you see, no one gives damn. If it's not on "Ellen" or "The View" it's not real. To read more and view the video, click here.