Congress held its first hearing in half a century overnight on unidentified flying objects. And no, there is still no government confirmation of extraterrestrial life.

Testifying before a House Intelligence subcommittee, Pentagon officials did not disclose additional information from their ongoing investigation of hundreds of unexplained sightings in the sky. But they said they had picked a director for a new task force to coordinate data collection efforts on what the government has officially labelled "unidentified aerial phenomena."

Ronald Moultrie, the undersecretary of defence for intelligence, said the Pentagon was also trying to destigmatise the issue and encourage pilots and other military personnel to report anything unusual they see.

"We want to know what's out there as much as you want to know what's out there," Moultrie told lawmakers, adding that he was a fan of science fiction himself. "We get the questions not just from you. We get it from family and we get them night and day."

Lawmakers from both parties say UFOs are a national security concern. Sightings of what appear to be aircraft flying without discernible means of propulsion have been reported near military bases and coastlines, raising the prospect that witnesses have spotted undiscovered or secret Chinese or Russian technology.

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But the sightings are usually fleeting. Some appear for no more than an instant on camera — and then sometimes end up distorted by the camera lens. The US government is believed to hold additional technical information on the sightings that it has not disclosed publicly.

An interim report released by intelligence officials last year counted 144 sightings of aircraft or other devices apparently flying at mysterious speeds or trajectories. In all but one of the sightings investigated, there was too little information for investigators to even broadly characterise the nature of the incident.

A top Pentagon official briefly demonstrated the challenge. Scott Bray, deputy director of naval intelligence, stood next to a television to show a short video taken from an F-18 military plane. The video shows a blue sky with passing clouds. In a single frame — which it took several minutes for staff in the room to queue up — there is an image of one balloon-like shape.

"As you can see, finding UAP is harder than you may think," Bray said, using the acronym for "unidentified aerial phenomena."

Rep. André Carson, an Indiana Democrat who chaired the hearing, called on investigators to show they "are willing to follow the facts where they lead."

Rep. Rick Crawford, an Arkansas Republican, noted that the investigations were not "about finding alien spacecraft but about delivering dominant intelligence."

"The inability to understand objects in our sensitive operating areas is tantamount to intelligence failure that we certainly want to avoid," he said.