'TMZ Investigates: UFOs: The Pentagon Proof' Now Available to Stream on YouTube

Our deep dive into the first-ever declassified Pentagon report detailing 144 accounts of UFO sightings is officially up on YouTube ... and there's a lot to unpack.

"TMZ Investigates: UFOs: The Pentagon Proof" analyzes our government's official response to UFO conversations from an investigative standpoint ... we interview key players and showcase footage of UFOs recorded from all over the world.

We talked to military officials and pilots who say they suffered severe retribution for daring to implore the Pentagon to take UFOs seriously ... including former Pentagon Counterintelligence official Lue Elizondo.

Lue appeared on camera and explained how Pentagon officials threatened to pull his security clearance, called him a liar and smeared his name ... all because he was pushing for UFO transparency.

Meanwhile, former Navy Pilot Ryan Graves told us he saw plenty of UFOs during his time in the sky, but said a lot of pilots wouldn't speak out about their own experiences for fear of being called crazy and having their reputations ruined.

Plus, former Defense Department official Christopher Mellon, who has spoken out about government findings and sightings, told us his career was placed in jeopardy by pressing the UFO issue. Still, he said he's willing to accept those consequences given what's at stake.

We also spoke with UFO journalists Jeremy Corbell and George Knapp ... and they break down one of the biggest mysteries to ever face mankind