It said in January that some briefing material it had about the videos was classified as top secret and would cause "exceptionally grave damage to the National Security of the United States" if released.
Despite long-standing popular associations with stories of aliens, the terms "unidentified aerial phenomena" and "UFO" do not mean the object is thought to be extraterrestrial.
Take a look at the videos — which have the file names FLIR, GOFAST, and GIMBAL — below.
FLIR, also known as the Nimitz video, November 2004
It has also been called the Nimitz video, from the name of the pilots' ship, the USS Nimitz, according to Vice.
FLIR has no pilot commentary but shows a dark, oblong shape being tracked by the infrared camera. At one point, the object accelerates unexpectedly to the left, causing the sensor to lose its fix on it.
"It accelerated like nothing I've ever seen," one of the pilots, Cmdr. David Fravor, told The Times in 2017.
GOFAST, January 2015
This clip shows what looks like the ocean surface as a small object skims past the camera at high speed.
The pilots tracking it can be heard giving a whoop of satisfaction when the camera gets a fix on it. One says, "What the f--- is that?"
GIMBAL, January 2015
In the 34-second footage, the aircraft's infrared camera tracks a saucer-like object flying above clouds as pilots discuss what it could be.
One says it could be a drone, while another comments that "there's a whole fleet of them," though no other object is visible in the video.
The object then rotates.
"My gosh, they're all going against the wind — the wind's 120 knots to the west," the first pilot can be heard saying.
The Department of Defense said on Monday that it found that the videos don't "reveal any sensitive capabilities or systems" and that their release "does not impinge on any subsequent investigations of military air space incursions by unidentified aerial phenomena."
"DOD is releasing the videos 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," it added.
"The aerial phenomena observed in the videos remain characterized as 'unidentified.'"
This release 'only scratches the surface' of what the government knows
Former Sen. Harry Reid, who helped fund the US government's UFO investigations, tweeted on Monday that the Pentagon's release of the videos "only scratches the surface" of what the government has on file.