Why Do Boeing Plane Models Start & End With The Number 7?

The names of American manufacturer Boeing’s commercial aircraft are known for beginning and ending with the number seven? Starting with the 707 in the 1950s, Boeing has decades of developing popular jetliners with catchy-sounding numerical designations under its belt. But what is the reason for this numbering system?

Lufthansa, Boeing 707, Saviour Attempt
Pan Am introduced the Boeing 707 in October 1958.  Photo: Getty Images

Theories about Boeing’s numbering

There are a handful of interesting theories that have surfaced regarding Boeing’s numbering system. One of these is the idea that the 707 was Boeing’s seventh aircraft series. However, this was not the case. Boeing’s first ‘modern’ passenger jetliner was the 367-80. This came before the 700 series, although it was a prototype for the 707.

Another, perhaps slightly more optimistic, idea is that 707 represented the number of passengers it carried. This presumably stems from Airbus having named its A300 after its approximate capacity (which, in reality, went as high as 345). However, this was not the case for the Boeing 707. Even at its exit limit, the largest variant (707-320C) held just 219 passengers.

The real reason

The actual reason for Boeing’s numbering system is for ease of reference. An aircraft’s identifying number helps engineers to differentiate between various products in the Boeing portfolio. Its full designations are as follows.

KLM Boeing 777-300ER Orange Pride
The Boeing 777, or ‘triple-seven,’ takes the trend a step further! Photo: Vincenzo Pace | Simple Flying

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  • 100 for earlier models. Boeing no longer utilizes this designation, but did retrospectively for the very first biplanes it built.
  • 200 for early single-wing designs that deviated from the contemporary biplane trend.
  • 300 and 400 for commercial propeller-driven aircraft.
  • 500 for turbo-engined aircraft.
  • 600 for missiles and rocket-powered devices.
  • 700 for jet-powered commercial aircraft.
  • 800 is presently unused.
  • 900 for boats. Boeing constructed a turbojet hydrofoil, which it designated as 929.

There was technically another series, known as the Boeing 2707. This was a proposed American competitor to the supersonic European airliner Concorde. However, Boeing never ended up producing this aircraft.

Why do 700 series aircraft also end with a 7?

A second question to the above is why 700 series aircraft also end with a seven. How different would the world be if airlines had flown thousands of passengers across the Atlantic on Boeing 740 aircraft every day? Does a Boeing 780 Dreamliner sound more or less dreamy?

Boeing 929 Hydrofoil
A Boeing 929 hydrofoil vessel in Hong Kong. Photo: Daniel Case via Wikimedia Commons

Hopefully, these examples show why Boeing made the change. From a marketing perspective, it is more attractive on paper to have the symmetry of 7×7, rather than the formulaic but asymmetrical 7×0. In spoken discourse, it also rolls off the tongue nicely, and is easier for even non-avgeek passengers to remember designations of legendary aircraft such as the 747.

Possible future designations

It is interesting to consider how Boeing might number its commercial aircraft in the future. After all, it appears to have somewhat backed itself in a corner by developing so many jetliner families over the years. The numbers it has already deployed are as follows.

  • 707, 717, 727, & 757 have been discontinued.
  • 747 is unlikely to have another model number beyond the current 747-8.
  • 777 and 787 are new enough that they will continue to have more versions built.
  • 737 will also likely be around for a while. Interestingly, it has gone through all the sub-variants from -100 to -900, hence the newest series is referred to as the MAX.
Boeing 747 Heathrow Sunset Getty
Boeing’s numbering system serves as a useful marketing tool that gives aircraft more memorable designations for airline executives and passengers alike. Photo: Getty Images

Therefore, as it stands, the only number free is the 797, which has long been rumored to be a new middle-market aircraft. Beyond that, Boeing has no more numbers that will fit in with its current trend.

In the future, it may need to add a fourth number to the front of its designation, like with the proposed Boeing 2707 in the 1970s. Alternatively, it could move beyond a seven at the end of the number, to give titles such as 748. It may even find that it has to move up to a new series, such as the presently unoccupied 800.

What are your thoughts about this numbering process? et us know what you think in the comment section.