(NewsNation) — A former Navy fighter pilot says a whistleblower’s claim that the U.S. government is withholding information about “non-human origin” spacecraft is “believable” and must be investigated by Congress.

Lt. Ryan Graves was the first active duty pilot to testify before Congress about his squadron’s experience with unidentified craft, officially classified by the government as Unidentified Aerial Phenomenon (UAP).

“His story is believable, and I think it’s now up to Congress to verify it and communicate the results of that to the American people,” Graves said in response to the claims Monday on “Elizabeth Vargas Reports.”

The whistleblower is David Grusch, an Air Force veteran and former member of the All Domain Anomaly Resolution Office task force.

In his role within the U.S. defense establishment, 36-year-old Grusch said he was trusted with some of the government’s most intimate secrets.

In his time at the UAP task force, Grusch said the group was refused access to a crash retrieval program.

“These are retrieving non-human origin technical vehicles, call it spacecraft if you will, non-human exotic origin vehicles that have either landed or crashed,” Grusch said.

During his time as a Navy pilot, Graves witnessed a UAP, which he described as “dark gray or black cubes inside of clear spheres” that were spotted on a near-daily basis. He founded an advocacy group, Americans for Safe Aerospace, to encourage other pilots to come forward with sightings and lift a veil of secrecy.

“I still believe that there is secrecy and stigmas associated with this topic, and this conversation that we’re having today I think is a massive step in the right direction,” Graves said.

Even though the conversation may have shifted over the past several years, Graves said pilot reports of sightings typically end at air traffic control.

Graves, who is also serving on a NASA panel studying UFOs, previously told NewsNation more information is needed to move the conversation forward. That NASA panel held its first public meeting in April.

“It was a bit disappointing to hear the FAA representative at the public meeting … state that he was only familiar with maybe four or five reports of UAP from their FAA controllers,” Graves said. “I’m personally hearing reports from pilots that they’re seeing objects on almost a nightly basis off the northern Pacific, as well as the northern Atlantic.”

Grusch alleges the U.S. government has recovered non-human craft for decades. He recently filed a whistle-blower complaint, stating he gave what he referred to as classified “proof” to Congress and the Intelligence Community Inspector General.

“If these objects are flying around and have been for a number of years, the assumption would be that they would likely crash at some point and there would be an operation to retrieve it,” Graves said.

As for the veracity of Grusch’s claims, Graves said the onus is now on Congress to look into the matter.

“It’s not about trusting him, it’s the fact that he’s brought evidence forward that we can go forward and verify, and that’s now in the hands of Congress to be able to go and verify that story,” Graves said.

NewsNation senior national correspondent Brian Entin contributed to this report.