WASHINGTON — Two Navy veterans who claim to have seen unidentified aerial phenomena, better known as UFOs, joined a Pentagon whistleblower Wednesday to warn Congress that the sightings threaten national security and are being kept secret.

Ryan Graves, a former Navy F-18 pilot, and David Fravor, a retired Navy commander, described their encounters with strange, flying objects at a crowded hearing before the House Oversight Committee, which is leading a push by lawmakers to destigmatize reporting on such incidents and increase government transparency about potential alien life.

“As we convene here, UAP are in our airspace, but they are grossly underreported. These sightings are not rare or isolated, they are routine,” Graves said. “Parts of our government are more aware about UAP than they let on, but excessive classification processes keep crucial information hidden.”

Graves said he first became aware of UAPs in 2014, after upgraded jet radar systems used by pilots stationed at Naval Air Station Oceana in Virginia Beach, Va., began detecting unknown objects. A pilot soon saw one in person, observing a floating “dark gray cube inside of a clear sphere” during a training mission about 10 miles off the Atlantic coast, Graves said.

There was no official acknowledgement of the incident, and it was never investigated, he said.

“If everyone could see the sensor and video data I witnessed, our national conversation would change,” Graves said. “If UAP are foreign drones, it is an urgent national security problem. If it is something else, it is an issue for science. In either case, unidentified objects are a concern for flight safety.”

The Pentagon last year established the All-domain Anomaly Resolution Office to investigate reports of such phenomena, looking into more than 800 sightings. The U.S. government has attributed most of the reports to balloons, drones, birds, weather events and litter such as plastic bags, but many remain unexplained.

Graves estimates only about 5% of UAP sightings are being reported due to risk of professional repercussions. Most witnesses are commercial pilots for major airlines who have seen UAPs at 40,000 feet “making inexplicable maneuvers, like right-hand turns and retrograde orbits or j-hooks,” Graves said. The pilots are primarily seeing dark gray or black cubes inside of clear spheres, he said.

Fravor, a retired commanding officer of the Navy’s “Black Aces” strike fighter squadron, told lawmakers that he saw a white object shaped like a Tic Tac candy after launching his jet from the USS Nimitz aircraft carrier in 2004. He spotted the object “moving very abruptly” off the California coast before rapidly climbing up to about 12,000 feet in the air, then disappearing and reappearing 60 miles away less than a minute later.

“I never felt that we were alone with all the planets out there, but I wasn’t a UFO person,” Fravor said. “I think what we experienced [that day] was well beyond the material science and capabilities that we had at the time, that we have currently and or that we’re going to have in the next 10 to 20 years.”

David Grusch, a former intelligence officer with the Air Force, alleged under oath Wednesday that the U.S. government has for decades maintained a program that collected and attempted to reverse engineer crashed UFOs. He came forward as a whistleblower last year and said he has suffered “very brutal” retaliation for his decision and fears for his life.

He claimed “non-human biologics” have been found at the alleged crash sites and said he knows of “people who have been harmed or injured” because of government efforts to cover up information about the UFOs.

“I am hopeful that my actions will ultimately lead to a positive outcome of increased transparency,” Grusch said.

The Pentagon has denied the allegations. Sean Kirkpatrick, the director of the All-domain Anomaly Resolution Office, told senators in April that there is “no credible evidence thus far of extraterrestrial activity, off-world technology or objects that defy the known laws of physics.”

Congressional interest in the issue has nonetheless surged in recent years with a House panel last summer holding the first public hearing on UFOs in more than 50 years. Wednesday’s oversight hearing was called by lawmakers who said they were frustrated by the shroud of secrecy around reported sightings.

“This is an issue of government transparency,” said Rep. Tim Burchett, R-Tenn. “We’re not bringing little green men or flying saucers into the hearing — sorry to disappoint about half y’all — we’re just going to get to the facts.”

Burchett said the Defense Department, intelligence community and NASA, which is set to publish its report on UAPs in the summer, declined to participate in the hearing. Rep. Anna Paulina Luna, R-Fla., said lawmakers who recently traveled to an Air Force base in Florida to investigate reported UAP sightings by military pilots were stonewalled by the Pentagon.

“We are simply told not to question the government and that the government has it under control,” she said.

The Senate this week is expected to vote on an amendment to the annual defense policy bill that will force the government to disclose reported sightings and declassify records related to UAPs.

“For decades, many Americans have been fascinated by objects mysterious and unexplained," said Senate Majority Leader Chuck Schumer, D-N.Y. "It’s long past time they get some answers."

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