WASHINGTON — A House subcommittee opened a hearing on Tuesday on unidentified aerial phenomena observed by military pilots and others, pledging to bring transparency to an investigation of unexplained reports that have long been shrouded in stigma, confusion and secrecy.

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.”

Members of Congress have also been frustrated, with some suggesting that the Pentagon has 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.

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.

The subcommittee will hear from two senior Pentagon officials: Ronald S. Moultrie, the Defense Department’s under secretary for intelligence, and Scott W. Bray, the deputy director of naval intelligence.

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. Today, we know better. U.A.P.s are unexplained, it’s true,” he said, referring to unidentified aerial phenomena. “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.