Military aircraft typically carry two identification numbers—the manufacturer's model number and the corresponding military designation. To further obscure things, since 1924 there have been three distinct military numerical designation systems used and, occasionally, the same letter has been used for different purposes in different systems. To relieve this confusion, I will attempt to explain what may seem to the uninitiated to resemble a random concoction of numbers and letters.

A basic understanding of the military and Cessna number and letter identification systems will help to make sense out of apparent chaos. I will not try to provide an exhaustive reference, but will offer sufficient detail to familiarize the reader with the various schemes and enable the reader to interpret the designations appearing in subsequent chapters.

Cessna model number identification began simply, with the first design referred to only as Cessna Design Number 1. In 1931, Cessna began using a two letter code with its "A" series and "B" series—with a second letter used to indicate the installed engine, thus the AW was an A model with power by Wright. However, Cessna soon deviated from their own scheme with the DC-6 series—the DC-6 being powered by Curtiss and the DC-6A and DC-6B powered by Wright engines. The nomenclature "CG" was used for Cessna Gliders produced during the early 1930s.

In 1934, Cessna shifted to a single letter "C" followed by two digits to represent the year the design was started—the C-34 was designed in 1934 and the C-37 in 1937. This was changed again, in 1938, with new model numbers corresponding to engine horsepower—the C-145 was an Airmaster with 145 horsepower, and the C-165 an Airmaster with 165 horsepower. However, the T-50 designation of 1938 seems to have been derived from the fact that this was a twin-engine aircraft with seating for five.

After World War II, Cessna adopted a new numbering system, which continued to evolve through 1961. The low-powered, single-engine aircraft became the "100" series (C-120, C-152, C-185, etc.), the higher-powered singles became the "200" series (C-210, for example), light twins composed the "300" series (like the C-310), heavier twins formed the "400" series (C-404), and the jets the were eventually assigned to the "500" series (the Citation series). The 400- and 500-series were not yet a part of the new scheme when the T-37 jet trainer was designed, so the twin-engine airplane was christened the Model 318.

Cessna used a single-letter suffix to indicate a significant change for a specific model year—thus the 1961 152A became the 1962 152B. The suffixes "O" and "I" were generally not used, to avoid confusion with zeroes and ones. A prefix letter usually indicated a more major change—consequently, the 150K Aerobat became the A150K and the Cessna-Reims 172E became the R172E.

If the constantly shifting designations used by Cessna over the years is perplexing, THEN the equally volatile military scheme can be even more confusing. Since 1924, the military model identification method has retained the basic organization of the original scheme:

However, the meaning of the letters used for the Status Prefix and Type Symbol has changed several times over the intervening years. The system adopted in 1924 included the following Type Symbol definitions: