UFOs are about to make their way to the U.S. Senate. Here's what to know.

U.S. intelligence agencies are expected to deliver a report on “unidentified aerial phenomena” to Congress next month, sparking renewed interest and speculation into how the government has handled sightings of mysterious flying objects — and if there's any worldly explanation for them.

The unclassified report, compiled by the director of national intelligence and the secretary of defense, aims to make public what the Pentagon knows about unidentified flying objects and data analyzed from such encounters.

While UFOs have been part of American mythology for decades, this report is different. Legitimate debates over UFO sightings have gained traction in recent years after several leaked photos and videos from the U.S. Navy appeared to show mysterious flying objects in American airspace.

Last year, the Pentagon declassified three such videos captured by Navy pilots, intensifying speculation over the incidents, which have been confirmed by pilots who have observed them and even presidents who have been briefed on them.

Here’s how UFO sightings jumped from the realm of science fiction to the halls of Congress.

What do we know so far?

In August, the Department of Defense established the Unidentified Aerial Phenomena Task Force to investigate and “gain insight” into the “nature and origins” of unidentified flying objects. Earlier that year, the Department of Defense declassified three videos taken by Navy pilots — one from 2004 and two from 2015 — that showed mysterious objects flying at high speeds across the sky.

“The aerial phenomena observed in the videos remain characterized as ‘unidentified,’” Pentagon officials said in a statement at the time.

The three videos had leaked years earlier, but Pentagon officials said they declassified the footage to “clear up any misconceptions by the public on whether or not the footage that has been circulating was real, or whether or not there is more to the videos.”

A separate leaked Navy video, captured in July 2019, showed a sphere-shaped unidentified object flying over water near San Diego. The footage, obtained by a documentary filmmaker and shared with NBC News, appeared to show the mysterious object flying for a few minutes before disappearing into the water.

And on Sunday, two former Navy pilots were interviewed by “60 Minutes” on CBS News about a UFO sighting over the Pacific Ocean in 2004. Cmdr. Dave Fravor and Lt. Cmdr. Alex Dietrich spotted the unidentified object during a training exercise but were unable to classify it. Fravor described it as a “little white Tic-Tac-looking object,” adding that it lacked conventional exhaust plumes and had no wings or visible markings.

It also moved erratically, the pilots said.

In an interview with NBC News that aired in February, Fravor described the 2004 encounter, calling the object “the strangest, most obscure thing I’ve ever seen flying.”

“As soon as we looked down, we see the whitewater, and then we see this little white Tic Tac,” Fravor told NBC’s "The Overview." “It’s pointing north-south and it’s just going forward, back, left, right,” he said, adding that it was bouncing around “like a ping-pong ball.”

Fravor said he approached the mysterious object to take a closer look, and it began mirroring his movements. When the pilot got to within a half-mile of the UFO, it suddenly vanished, he said.

When did this all start?

Interest in UFO sightings, particularly by the military, is not new.

In 2007, the U.S. Defense Department quietly established the Advanced Aerospace Threat Identification Program, which was designed to investigate UFO sightings. The secret $22 million initiative was shut down in 2012, and its existence was acknowledged for the first time in December 2017, following a report about the program published by The New York Times. The Times reported that the program’s initial funding came largely at the request of former Senate Democratic leader Harry Reid.

In 2019, the Navy put together new guidelines for pilots to report “unidentified aircraft,” in a bid to formalize a process to investigate these types of mysterious sightings. The updated guidance came as a response to “a number of reports of unauthorized and/or unidentified aircraft entering various military-controlled ranges and designated air space in recent years," Navy officials told Politico in a statement at the time.

What is a UFO?

While UFOs are often synonymous with “aliens” in pop culture, the designation is not necessarily about extraterrestrials. An unidentified flying object is simply any object that can’t be classified as a known aircraft.

Several of the UFO sightings reported by Navy pilots were of unusually shaped objects that flew at high velocities, often maneuvering around in ways that baffled aeronautics experts and with no visible propulsion.

But aliens aside, the Pentagon has been interested in UFOs because they could pose threats to national security. Lt. Ryan Graves, a former Navy pilot, told “60 Minutes” that pilots on training flights have seen unexplained phenomena “every day for at least a couple years.”

“I am worried, frankly,” Graves said in the “60 Minutes” interview. “You know, if these were tactical jets from another country that were hanging out up there, it would be a massive issue. But because it looks slightly different, we’re not willing to actually look at the problem in the face. We’re happy to just ignore the fact that these are out there, watching us every day.”

Whether the UFO sightings are the result of advanced technology from foreign adversaries or if they have more bizarre, otherworldly origins, government officials need to have the facts, said Luis Elizondo, a former senior intelligence officer and the former director of the Advanced Aerospace Threat Identification Program.

“They have the responsibility to always act in a manner that is in the best interest of the United States and the American people,” Elizondo told NBC News. “This topic is no different than any other national security issue, and we must remain diligent, deliberate and discerning.”

Why is this happening now?

The report that will be delivered to Congress in June is the result of a provision in the $2.3 trillion coronavirus relief and appropriations bill that President Donald Trump signed last year. The stipulation called for a “detailed analysis of unidentified aerial phenomena data and intelligence” from the Office of Naval Intelligence, the Unidentified Aerial Phenomena Task Force and the FBI.

Some senators are pushing other lawmakers and government officials to do more to investigate encounters with mysterious flying objects.

“I want us to take it seriously and have a process to take it seriously,” Sen. Marco Rubio, R-Fla., told “60 Minutes.”

Rubio’s comments add support to other calls to treat possible UFO sightings with legitimacy rather than as fringe beliefs, a recent shift that was the subject of a feature story in The New Yorker titled “How the Pentagon Started Taking U.F.O.s Seriously.”

Christopher Mellon, a top defense official who served in the administrations of Presidents Bill Clinton and George W. Bush, said more needs to be done, adding that the process for reporting UFO sightings should be destigmatized.

“My hope is that this administration will provide our military people the support they deserve,” Mellon told NBC News. “On this issue, that means determining ASAP what threat if any is posed by the unidentified vehicles that are brazenly and repeatedly violating restricted U.S. airspace over hovering around our warships. Our people are naturally and rightly concerned and almost nothing has been done to address their concerns.”