Practically synonymous with high-altitude espionage, the Lockheed U-2 spy plane played an almost legendary role in the Central Intelligence Agency’s activities during the Cold War, so much so that a 1/6th scale model of the plane currently hangs in the Agency atrium in Langley, Virginia. The aircraft was notoriously difficult to pilot and physically demanding (flights of over ten hours at over 70,000 feet were not uncommon), and a formerly TOP SECRET manual uncovered in the Agency archives outlines a strict regimen to keep pilots fit and healthy.

Unsurprisingly, the manual touches upon the necessity of maintaining a proper diet …

but somewhat surprisingly, the purpose of this proper diet isn’t merely about a pilot getting their vitamins and minerals; it’s also about “obviating the need for frequent defecation.”

In other words, keeping pilots from soiling their flightsuit.

If you’re interested in giving the “high protein, low residue” diet a try, approved foods include eggs, rice, and lean meats …

while eschewing spicy foods, pickles, most vegetables, and, regrettably, all cheeses except cottage.

A sample meal was provided, and it will look familiar to anyone who grew up watching cereal commercials and wondered exactly who was eating this “balanced breakfast” they kept talking about.

While the manual makes it clear that pilots who’ve strayed from these guides should not be cleared to fly, the one exception is cases where there has been a “significant time lapse” between the last meal and a scheduled flight. In those cases, the pilot is allowed a snack of milk and cookies …

which, as the manual notes, can be provided with a “minimal amount of preparation and effort.”

Now, U-2 pilots do not live off of sugar cookies alone, and while the CIA manual makes it clear that any use of alcohol in the lead up to a flight is verboten, another manual in CREST, from the Air Force’s U-2 program, is a little more forgiving. Pilots were permitted a small amount of liquor the evening before a morning flight …

though beer was still barred due to its “gas-forming tendencies.”

And if you’re wondering if the last half century’s advances in suit-soiling technology have given pilots license to avoid cottage cheese, that doesn’t appear to be the case; according to an article in Stars and Stripes, that same “high-protein, low-residue diet” was still in effect for U-2 pilots as of 2010.

Read the CIA’s manual embedded below.

Image via US Air Force