Reid arranged funding in 2007 to a US$22 million programme to investigate UFOs. The Pentagon confirmed its existence in 2017.
Reid tweeted: "I'm glad the Pentagon is finally releasing this footage, but it only scratches the surface of research and materials available. The US needs to take a serious, scientific look at this and any potential national security implications. The American people deserve to be informed."
Axios reports that the US Navy also confirmed an increase in UFO sightings in 2019. It introduced a new process to allow pilots to report sightings at the time.
Officials say that, while UFOs don't necessarily indicate extraterrestrial life, they raise concerns over aircraft flying near sensitive military facilities and military-controlled ranges.
The Navy is officially releasing them now, "in order to clear up any misconceptions by the public on whether or not the footage that has been circulating was real, or whether or not there is more to the videos," Pentagon spokesperson Sue Gough said in a statement.
"After a thorough review, the department has determined that the authorised release of these unclassified videos does not reveal any sensitive capabilities or systems and does not impinge on any subsequent investigations of military air space incursions by unidentified aerial phenomena."
CNN reports that the Navy videos were first released between December 2017 and March 2018 by To The Stars Academy of Arts & Sciences, a company co-founded by former Blink-182 musician Tom DeLonge that studies information about UFOs.
In 2017, a pilot who saw one of the UFOs in 2004 told CNN that it moved in ways he couldn't explain.
"As I got close to it ... it rapidly accelerated to the south, and disappeared in less than two seconds," said retired US Navy pilot David Fravor. "This was extremely abrupt, like a ping pong ball, bouncing off a wall. It would hit and go the other way."