Government officials testified Tuesday at Congress’ first public hearing on UFOs in more than 50 years as part of an ongoing U.S. effort to be more transparent about investigations into “unidentified aerial phenomena.”

UAPS are “a potential national security threat” and must be investigated, said Rep. André Carson, D-Indiana, chair of the House Intelligence Committee’s Counterterrorism, Counterintelligence, and Counterproliferation subcommittee.

“For too long, the stigma associated with UAPs has gotten in the way of good intelligence analysis,” Carson said. “Pilots avoided reporting, or were laughed at when they did. DOD officials relegated the issue to the back room, or swept it under the rug entirely, fearful of a skeptical national security community.”

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Sightings of UAPs have increased since the early 2000s as the stigma around reporting has decreased, according to Scott W. Bray, the deputy director of naval intelligence. A government database that tracks potential sightings has gained about 400 incidents since last June, when the U.S. Director of National Intelligence made public a report examining UAPs, he said.

The Navy and the Department of Defense have been working to transition from relying on anecdotes from aviators to a data-driven, “all hands on deck” approach to investigating the sightings, Bray said.

But Bray said it can difficult to identify the objects given that the sightings are often short and may not be recorded. He shared a few short videos and images of unidentified objects to demonstrate how fleeting the observations can be. 

One clip shot through night vision goggles off the United States coast several years ago showed glowing green triangles moving through the air. Investigators later determined the mysterious objects were unmanned aerial systems.

“This is a great example of how it takes considerable effort to understand what we’re seeing,” he said.

Members of Congress including Rep. Rick Crawford, R-Arkansas, stressed the importance of transparently while communicating the steps defense officials are taking to track and analyze unidentified objects in U.S. airspace.

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