If any of you amateur radio operators are tooling around in the ham universe and come across a very serious voice informing you that “Cadillac One is inbound,” we’d advise closing the channel — especially if you live in the vicinity of any major political institutions. There’s at least a fair chance you’ve tapped into U.S. Secret Service communications because Cadillac One is the informal nickname of the U.S. Presidential State Car, the limousine that carries the American Commander-in-Chief around.

If the U.S. National Security Agency finds you eavesdropping on Presidential security comms, they’ll either be very displeased or offer you a job. Either way, your life will likely become much more interesting in very short order. And we’re not limiting this advice to mere U.S. residents either, as Cadillac One often gets airlifted to other countries where the U.S. President is making an appearance. The same goes for (ironically) Marine One, one of a squadron of military helicopters used to transport the President by air over moderate distances. Indeed, by some measures, Marine One and the so-called Cadillac One exist largely to ferry the President back and forth to Air Force One, the specially modified jumbo airliner that serves as a flying miniature White House.

(Yes, calling a jumbo airliner “miniature” seems strange, but the 4,000 square feet of cabin space available on the modern Air Force One is positively tiny compared to the 55,000 square feet available in the actual White House.)

While any plane carrying the President of the United States is, by protocol, designated Air Force One, when most people use that term, they’re referring to one of two modified Boeing VC-25s, which are variants on the Boeing 747-200B. With their signature blue-and-white livery — developed by designer Raymond Loewy to mimic the typeface of the Declaration of Independence — these jets are known worldwide as symbols of the American Presidency. However, when the U.S. President isn’t aboard, these craft are often referred to by either their tail numbers — 28000 or 29000 — or by a conventional flight number, just like any other aircraft traveling through controlled airspace.

Moreover, prior to 1953, even if an aircraft was carrying a U.S. President, it was still known by its standard Air Force flight number. It wasn’t until that year that anyone discovered a need for the call sign Air Force One — and it was a very pressing need, at that.

WHY WAS THE U.S. PRESIDENTIAL AIRCRAFT GIVEN THE CALL SIGN AIR FORCE ONE?

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In 1953, President Dwight Eisenhower was flying aboard one of several presidential aircraft, a Lockheed VC-121E Constellation nicknamed Columbine II. The flight number for the President’s aircraft was Air Force 8610, which flight controllers briefly confused with Eastern 8610, an Eastern Airlines passenger flight. And by confused, we mean assigned to the same airspace, which is the first step towards a mid-air collision. Eisenhower, being shepherded by more-than-competent pilots, was never in any danger, because his crew immediately caught the error and informed flight controllers of the issue. To prevent any such future potential disasters, however, the unique call sign Air Force One was adopted for any plane carrying the U.S. President.

Thus was established the rule, which extended to both the call sign of the President’s helicopter, Marine One, and any fixed wing or rotary aircraft carrying the U.S. Vice President, which are known as Air Force Two and Marine Two, respectively.

That said, there are exceptions to this nomenclature. If either the President or Vice President is transported by any aircraft operated by branches of service other than the U.S. Air Force or U.S. Marine Corps, those craft are granted branch-specific call signs. For example, when hueys from the U.S. Air Force 1st Helicopter Squadron transport the Vice President, as is occasionally the case, these helicopters are granted the call sign Air Force Two.

Moreover, when President George W. Bush rode a Navy S-3 Viking jet to a carrier landing aboard the USS Abraham Lincoln, that flight inaugurated the call sign Navy One.

Prior to 1976, the U.S. Army shared primary Presidential helicopter transport duty with the Marines, and as such, any Army helicopter transporting the President was designated Army One.

Theoretically, if the President or Vice President ever flew aboard a U.S. Coast Guard helicopter or fixed-wing aircraft, either vehicle would inaugurate the call signs Coast Guard One or Coast Guard Two, but this has yet to actually happen.

President Richard Nixon is the only sitting U.S. President to ever fly in a civilian aircraft, as he did in 1973 to demonstrate confidence in the commercial airline industry during the energy crisis. While the President was onboard, the flight was known as Executive One. As members of the President’s or Vice President’s family often fly aboard civilian aircraft, these planes earn the call signs Executive One Foxtrot or Executive Two Foxtrot, respectively.

That’s not just some consistently careful classification, it’s a laboriously labeled example of executive Geek Trivia.

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