Government and military secrets can range from terrifying to amusing to downright absurd, but most are nothing short of intriguing. From a secret U.S. Air Force project to build a supersonic flying saucer to a now-famous World War II-era research program that produced the first atomic bombs to a plan to train domesticated cats to spy on the Soviet Union, here are 24 declassified military and CIA secrets.

Project 1794

In late 2012, the U.S. Air Force declassified a trove of documents, including records of a secret program to build a flying saucer-type aircraft designed to shoot down Soviet bombers. The ambitious program, called Project 1794, was initiated in the 1950s, and a team of engineers was tasked with building a disc-shape vehicle capable of traveling at supersonic speeds at high altitudes.

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The declassified documents reveal plans for the plane to reach a top speed of Mach 4 (four times the speed of sound), and reach an altitude of 100,000 feet (30,480 meters). The project’s estimated cost was more than $3 million, which in today’s dollars would be more than $26 million.

Read more: Live Science