WASHINGTON — Pentagon officials testifying at a House subcommittee hearing on Tuesday showed a previously classified video of an unidentified aerial phenomena, a fleeting color video of a reflective spherical object speeding past a military fighter jet.
The split-second image, shot through the window of an FA-18 fighter jet, shows a spherical object in the distance. The pilot also reported observing an object. The image, which remains unexplained, is an example of how difficult it is to determine what a short video clip may show.
Pentagon officials also played a video and displayed an image shot through night vision lenses that showed glowing green triangles moving through the air. The first video puzzled military officials. But the small triangles in the second recording, made years later, were determined to be drones.
“This time, other U.S. Navy assets also observed unmanned aerial systems nearby and we’re now reasonably confident that these triangles correlate the unmanned aerial systems in the air,” Scott W. Bray, the deputy director of naval intelligence.
The declassified videos were released as lawmakers pledged to bring transparency to an investigation of unexplained reports by miliary pilots and others that have long been shrouded in stigma, confusion and secrecy.
But Pentagon officials said they had to be careful not to reveal the precise abilities of military cameras and other sensors.
“We do not want potential adversaries to know exactly what we’re able to see or understand or how we come to the conclusion,” Mr. Bray said. “Therefore, disclosures must be carefully considered on a case-by-case basis.”
The Office of the Director of National Intelligence released a report last year, largely compiled by the military, cataloging unexplained aerial phenomenon dating to 2004.
The intelligence community criticized the document because it failed to draw conclusions or offer explanations for most of the events. Of the 143 episodes examined by the Pentagon, only one could be identified and categorized: “a large, deflating balloon.”
Mr. Bray’s remarks were aimed at trying to explain why it is so difficult to identify the images in the fuzzy videos. But lawmakers insisted on Tuesday that the Pentagon had been too dismissive of explanations.
“You need to show us, Congress and the American public, whose imagination you have captured, you are willing to follow the facts where they lead,” said Representative André Carson, Democrat of Indiana and the chairman of the House Intelligence Committee’s subcommittee that is holding the hearing.
“We fear sometimes that D.O.D. is focused more on emphasizing what it can explain, not investigating what it can’t,” he said. “I am looking for you to assure us today that all conclusions are on the table.”
Privately, many senior U.S. officials have been dismissive of theories suggesting that unknown objects captured in videos could be extraterrestrial aliens and insist there is no evidence that such explanations are probable.
Mr. Bray tried to stamp out some speculation that the phenomena were extraterrestrial in origin.
“We have detected no eliminations within the U.A.P. task force that is, that would suggest it’s anything nonterrestrial in origin,” Mr. Bray said, referring to unidentified aerial phenomena.
Representative Rick Crawford, Republican of Arkansas, said he was more interested in discussions of Russian or Chinese hypersonic programs than unidentified phenomena. But he said that it was important to identify the images.
The government’s inability to identify objects in sensitive operating areas was “tantamount to intelligence failure that we certainly want to avoid,” Mr. Crawford said. “It’s not about finding alien spacecraft.”
Officials are also skeptical that the phenomena could be some unknown Chinese or Russian technology, but concede it would be a significant concern if they were. That possibility, lawmakers and officials have said, is why the phenomena need to be examined more carefully.
“When we spot something we don’t understand or can’t identify in our airspace, it’s the job of those we entrust with our national security to investigate and report back,” Representative Adam B. Schiff, the California Democrat who leads the Intelligence Committee, said on Tuesday.
Unidentified aerial phenomena is the term that the federal government prefers over unidentified flying object, or U.F.O.
Congress last held a public hearing on the issue decades ago, after Project Blue Book, the Air Force’s flawed effort to investigate reports of alien sightings, which inspired generations of television programs.
After the report last year, intelligence officials pledged to renew their efforts. Prompted by Congress, the Pentagon overhauled its task force for looking into the unexplained events, calling it the Airborne Object Identification and Management Synchronization Group.
In his opening remarks, Mr. Carson criticized the Pentagon for failing to name a director to lead the new task force and pledged to bring “the organization out of the shadows.”
Military officers who were too embarrassed to report unexplained phenomena had impeded “good intelligence analysis,” Mr. Carson said.
“Pilots avoided reporting or were laughed at when they did. D.O.D. officials relegated the issue to the back room or swept it under the rug entirely, fearful of a skeptical national security community,” he said. “Today, we know better. U.A.P.s are unexplained, it’s true. But they are real. They need to be investigated. And any threats they pose need to be mitigated.”
Not all experts are convinced. Mick West, a science writer who has focused on debunking conspiracy theories, said some of the objects seen in the videos recorded by the military have plausible — and dry — explanations that are far more likely than any kind of extraworldly technology.
Some strange movement could be attributed to movement by the sensor, Mr. West said. Other videos showing fast movement could be an optical illusion, and others could be caused by glare.
