Understanding and assessing the reports is another matter. The spontaneous and often quick nature of the incidents means that officials frequently have little data to work with.
During the hearing, Bray pointed to footage of a mysterious object zooming by a military aircraft, appearing and disappearing in the blink of an eye.
"I do not have an explanation for what this specific object is," he said.
Lawmakers asked Bray to play and replay the video so they could catch a glimpse of the puzzling visual captured through a plane's window.
In another video, Navy personnel documented a triangle flashing off the coast of the United States. Several years later, Navy personnel witnessed another triangle floating off a different coast in the U.S., Bray said.
"We're now reasonably confident that these triangles correlate to unmanned aerial systems in the area. The triangular appearance is a result of light passing through the night vision goggles and then being recorded by an SLR camera," he said. "This is a great example of how it takes considerable effort to understand what we're seeing in the examples that we are able to collect."
