From Episode 1:

Resignation letter of Luis Elizondo

Why did Luis Elizondo, director of the Pentagon's hush-hush program investigation UAPs, or unidentified aerial phenomena, step down from his post? "It was because of my allegiance to the Department of Defense and the American people," Elizondo told HISTORY. For the full letter, read below:

From Episode 1:

Tic Tac UFO Executive Summary

This Executive Summary of the 2004 USS Nimitz “Tic Tac” event was obtained by investigative journalist George Knapp, from KLAS-TV Las Vegas. According to Knapp, the 2009 report was created for the U.S. military and includes statements from seven Navy pilots as well as radar operators. The summary notes the advanced sensors used to detect the Tic-Tac shaped craft, the exact location of Commander David Fravor’s intercept and the Tic Tac’s extraordinary capabilities. CLICK HERE TO SEE THE REDACTED 13-PAGE REPORT.

From Episode 2:

Map of UFO Hot Spots

UFO Sightings Hot Spots

This map was adapted from a brief created for the Deputy Secretary of Defense in 2009. It gives a birds-eye view of the UFO activity near Department of Defense and foreign military facilities over the last several decades.

From Episode 3:

Map of Baja California UFO Hot Spot Near the USS Nimitz Incident

Map of USS Nimitz-related UFO sightings off the coast of Baja

This map, created for Episode 3 of "Unidentified," shows nearly a dozen incidents of unexplained aerial phenomena that appeared off the coast of Southern California and Baja California, Mexico. The 2004 sightings reflect those reported by pilots and radar operators of the USS Nimitz Carrier Strike Group during a weeklong incident. Other points on the map show sightings by local Mexican fishermen and pilots near Guadalupe Island, 150 miles off the Baja California coast. The location corresponds to the latitude and longitude identified by a senior radar operator in the Nimitz group as the spot where the UFOs his team were tracking fell off the radar. The U.S. Navy conducts training exercises off the Southern California coast, and Guadalupe Island is home to a Mexican military weather station. 

From Episode 105:

Witness Reports from 2003 North Dakota UFO Sighting

HISTORY's Unidentified: North Dakota Materials

CLICK HERE TO READ official police statements, handwritten reports and sketches of UFOs sighted in McClusky, North Dakota, some 60 miles south of major nuclear facilities in Minot. N.D.

From Episode 106:

Studies done by the Pentagon-based AATIP Advanced Aerospace Threat Identification Program  

Illustration from the AATIP study entitled 'Traversable Wormholes, Stargates, and Negative Energy'
Artist's rendering from the AATIP study entitled 'Warp Drive, Dark Energy, and the Manipulation of Extra Dimensions'

In January 2019, the U.S. Defense Intelligence Agency disclosed that a now-defunct program under its auspices called AATIP, or the Advanced Aerospace Threat Identification Program, conducted research on topics such as wormholes, warp drive and other areas of unconventional science as part its mandate to identify and track space-based threats. The program was funded from 2007 to 2012, at the urging of then-Senate Majority Leader Harry Reid. For a full list of the 38 research titles funded by the program, CLICK HERE.