By Rob Russell
There have over the years been many theories about how Boeing came up with the 700 series for its modern-day commercial aircraft.
But one has to go back to the end of World War 2. Before the Second World War, the first Boeing aircraft that carried passengers designated the Model 80, represented Boeing in the commercial sky. At the time, the Seattle-based manufacturer built mostly military aircraft – that was the company’s bread and butter.
At that time, Douglas had a firm hold of the commercial aviation market with their DC-2 and DC-3. However, Boeing‘s commercial aircraft saw fairly limited success. Boeing mainly focused on military aircraft. Yet changes were about to come.
As the War came to an end and the need for military aircraft was being reduced, Boeing’s president named William Allen decided the company needed to diversify its portfolio. Apart from their various military orders, Allen decided that Boeing, in order to survive, needed to diversity and develop aircraft for commercial use. To avoid confusion within the company and when communicating with Boeing’s customers, the engineering department classified its products as follows:
300 and 400 were designated for commercial aircraft;
500 would mean turbo engines;
600 were allocated to the rockets and missiles departments;
And Boeing assigned the number 700 to jet engines.
Boeing developed the world's first large swept-wing jet, the B-47. That aircraft sparked interest in some of the airlines. One, in particular, Pan Am, asked Boeing to determine its feasibility as a commercial jet transport. At the same time, Boeing began studies on converting the propeller-driven model 367 Stratotanker, better known as the KC-97, into a jet-powered tanker that would be able to keep pace with the B-52 during in-flight refuelling.
Boeing product development went through several renditions of the model 367, and finally, a version numbered 367-80 was selected. It was soon nicknamed the "Dash 80." Boeing was keen to see a commercial jet take to the air, as McDonnell Douglas was busy developing a commercial jet and Boeing wanted theirs to be the first American-built jet into commercial service. (The British-built De Havilland Comet was the first commercial jet to take to the skies)
Boeing took a calculated risk by financing the development and construction of the Dash 80 prototype with its own funds. The goal was to put the aircraft into production as both an Air Force tanker/transport and a commercial jet transport. Since both of these offspring of the Dash 80 would be jet transports, the model number system called for a number in the 700s to identify the two new planes. The marketing department decided that "Model 700" did not have a good ring to it for the company's first commercial jet. So they decided to skip ahead to Model 707 because that reiteration seemed a bit catchier.
Following that pattern, the other offspring of the Dash 80, the Air Force tanker, was given model number 717. Since it was an Air Force plane, it was also given the military designation of KC-135. The number 717 was quickly dropped but did pop up further down the years when Boeing acquired the McDonnell Douglas company and named its variant of the DC9, the 717.
It was all very well having the 700 series assigned to commercial aircraft, but Boeing decided to take matters further and assigned another 3 numbers, eventually becoming alphanumeric to indicate the variant of the type and who owned it. It came up with an ingenious system whereby the first number would indicate the model variant and the last two were dedicated to customers. These last two numbers stuck with the customer and were attached to any model and variant the customer ordered. This first sequence of numbers started at 20 and ran until 99 (Caledonian Airways). The number 20 was reserved for Boeing’s own use.
Boeing soon ran out of numbers to allocate to customers, so the second sequence ran from 00 (again reserved for Boeing) to 19 (Air New Zealand), which also soon ran out!
The commercial department came up with a third sequence, which started with a letter and a number. This began at A0 (LAB Airlines, Bolivia) and ended at Z9 (Lauda Airlines). It was only a matter of time before all those were allocated to customers, so they introduced a fourth sequence! It was essentially the third sequence reversed, i.e. beginning with 1A (Martinair) and ending with 9U (Cokaliong Airlines).
It was only a matter of time, again, before that series ran out, so they introduced a fifth series, this time with two letters, beginning with AA (Alan Abrina Aircraft Leasing Corp.) and ending with ZW (Digong Duterte Airways).
So it was thus possible to work out from the numbers who owned the various aircraft flying around the skies. The first three numbers were the model numbers and the next three numbers were given to variant and customer. For example, a 707-100 ordered by Qantas, was given the designator 707-138. SAA ordered Boeing 727-100 series and these were designated as 727-144s. When SAA ordered their 747s, the first 200 series were Boeing 747-244s, likewise the SPs ordered by them were designated as 747SP-44s.
The number 36 was given to BOAC, subsequently, British Airways and their 747s were designated as 747-236 or 747-436.
The codes do not change if the aircraft is subsequently sold, such as if a passenger aircraft is converted into a freighter or owned and operated by another airline. For example, a Boeing Dreamlifter that was originally built as a 747-400 passenger aircraft for China Airlines with customer code 09 would be designated as 747-409(LCF).
Although in some cases if an airline cancelled or sold their order before Boeing had delivered the airframe, the customer code would be changed to that of the new purchaser. One such example is the order for sixteen 737-800s taken over by Qantas from American Airlines, after the American September 2022 in 2001 - these aircraft were delivered with Qantas' 38 code rather than 23 for American. But this was not the norm and a rare exception.
But after the fifth sequence, which ended in 2016, Boeing announced that they would no longer apply customer codes to any aircraft produced after a certain point, which would lead to their designators being the "generic" type for the model, similar to what Airbus had adopted with their various models. The codes were removed from the type certificates for each model with effect from the production line number shown below:
Boeing 737 Next Generation: line number 6082
Boeing P-8 Poseidon: line number 6020
Boeing 747-8: line number 1534
Boeing 767: line number 1102
Boeing 777: line number 1422
Furthermore, customer codes that have never been used for the 787 and 737 MAX and will also not be applied to the 777X either.