View Full Version : Boeing Numbering System, history

I. M. Esperto
10th Sep 2002, 19:54
I called Boeing, and asked how they came up with such names as the B-707.

I got this excellent reply.

I called Boeing PR in Seattle, and asked about the numbers

"Joyce" responded:


Your question about why Boeing uses the 707 / 727 / 737 / 747 / 757 / 767 / 777 designations for its airplanes is asked frequently. It developed as follows:

When the Boeing numbering system for its products began sometime after the company was founded in 1916, it was made retroactive to the first airplane, which became No. 1. From then on, products were grouped in series.

The series from 1 to 102 covered airplanes of various types, mostly biplanes. The 103 to 199 series was assigned to various airfoil sections in the engineering department. The 200 series designates airplanes in the ‘20s and ‘30s up to and including the famous B-17 bomber, which was 299. The 300 series included the Boeing 307 Stratoliner of 1938 (first pressurized passenger transport) the hugh Boeing 314 Clipper (seaplane), the B-29 and B-50 bombers and the double-decked 377 Stratocruiser series.

The 400 series was essentially the B-47 and B-52 jet bombers, the entire 500 series was reserved for industrial products including gas turbine engines, the 600 series was for GAPA and Bomarc (missiles) and the 800 and 900 model series were used by Boeing for hydrofoil boats, lunar orbiters, military prototype programs and so on.

To switch back to the 300 series: when the prototype 707 jet transport was being designed, it was disguised as a Stratocruiser derivative and so carried the engineering number 367-80. When it came time to unveil it and change it to a production program, the 700 series was created.

The first of the line, the name “707”, was picked simply because it was catchy. Since then it has been only to build on that base of publicity and continue the naming sequence.

The numbers are assigned in the order the airplanes are designed, not by the numbers of engines or even dates of introduction. Hence, the 727, which came before the 737, has three engines, while the 737 has only two. The 757 and 767 were designed concurrently, although the 767 was introduced to passenger service in late 1982, while the 757 came on the air transport scene in early 1983.

Now the 777 line, a large, wide-body twin, was launched in October 1990. Will our next commercial transport series beyond the 777 be the Boeing 787? We don’t know yet. But the number 7 definitely has been good for Boeing.

Boeing Commercial Airplanes

13th Sep 2002, 00:10
Boeing also has gone a step further by incorporating customer IDs into model numbers: For example, Pan Am was assigned customer #21, United #22, Lufthansa #30, TWA # 31, Qantas #38, Varig #41, Singapore Airlines #12, etc...
So, when it's a Boeing model 707-131, we would know that it was a dash 100 ordered by TWA. A Boeing model B777-312 would identify it as a B777 dash 300 series ordered by SQ. Since there are more than 99 Boeing customers, the company had expanded its customer identification numbers into alpha numerics. "J9" for example was assigned to the former Imperial Iranian Air Force. A Boeing 747-2J9F would identify it as a dash 200 Freighter.

13th Sep 2002, 17:30
I never knew that! Another mystery solved there.

But what about the 'odd one out': the 717? We all know that it was a MD design with a proper MD number, but that's not what I'm asking. I know that there is a story about the reason why the designation 717 was not used after they built the 707, I just cannot remember it fully. It probably hinges around the KC-135, something about how that one took up the 717 designation, which would explain why 727 and 737 were next. Can anyone confirm/deny/elaborate on this?

Also there was of course the 720: a 707 derivative. Another odd one out in the Big Boeing Numbering system!


PS: KLM has customer no. 06, and BA is no. 36.

I. M. Esperto
13th Sep 2002, 17:46
The B-707-131B was my first PIC aircraft.

I loved it. No other since had performance like she had.

13th Sep 2002, 19:29
Yes. I've heard that the 717 was indeed the KC-135 originally...

I think the customer order number was an excellent system. Mind you, got a bit confusing when aircraft were being brought by the multitude by leasing companies with their own number and then operated by carriers!

Several years ago I sat in a camoflagued 707 cockpit on a trailer outside Kermit's place at Tamiami - from the reg it was an old Pan Am machine, reg might have been N707PA, probably scrapped at KMIA - only time I've ever sat in a big jet left seat. Played with the paint-worn throttles, moved the column and imagined just how many miles the old girl had done and where she'd been in her time... sad end, just a plaything for little kids - and big kids like me.


13th Sep 2002, 21:00
And the Boeing 2707 was..........??


Where did the B720 fit into this numerology?

13th Sep 2002, 22:39
The 2707 was to have been the SST model that had never left the drawing board.

The 720 was 8 feet shorter than the 707-100 series and was usually distinguished from its counterpart by not having the VHF antenna atop the vertical fin and by having only one overwing emergency exit instead of the usual two. Nevertheless, there were some high density seating versions built with double overwing emergency exits; and some international versions included the VHF antenna atop the vertical fin. Also, some 720s had optional brake cooling fans.

There also was a 707-200 series of which only five editions were built for Braniff. Braniff was customer number 27, so its model designation was: B707-227.

And Qantas' 707-138s were special "long range" editions featuring additional fuel tanks.

The 707-400 series were powered by Rolls Royce Conways.

17th Sep 2002, 11:02
It could well have been N707PA you were 'playing' in, I'm very envious. It would feel a bit strange sitting in that venerable girl. She was the second 707 off the production line (not counting the prototype 367) and was delivered to Pan Am in December 1958. She served with Pan Am until 1974 and was then used by a variety of operators through to 1980 when she was put into storage at Miami. She was broken up in 1988. I have a black and white photo of her when she was brand new with gleaming white paint, I'd be interested to see a few shots of her remains now.


17th Sep 2002, 19:10
Got me going now Bevok - bit of research called for!

Not listed in Bob Ogden's Book... Hmmm....

17th Sep 2002, 20:19
The Boeing 720 was originally designated the 707-20, then the 717-20 before the settled on the 720. This was before they decided they liked the alliteration of the 7X7 format.

The formal designation of the Braniff 720 aircraft was the 720-027. Braniff also operated various marks of the 707, these being the: 707-138B, 707-227 and 707-327C.

Braniff operated both leased and owned versions of the 720. They initially ordered three with options for additional aircraft. Additional 720s were later leased from Aer Lingus airlines (720-048s). A 720-022 also snuck in, I'm not sure where from.

Onyl five 707-227’s were ever built, all for Braniff, but only four entering service. The first plane ship N7071 was lost during a pre-delivery test flight, when the crew became unable to control a “dutch-roll” condition.

Braniff later leased four long-range Boeing 707-138B’s from Australia’s Qantas airline in 1969. The –138B was the short-bodied 707 with the high-frequency antenna mounted on the top vertical stabilizer and a small fin on the underside of the aft fuselage between the horizontal stabilizers.

Braniff Fleet Register (http://www.braniffinternational.org/aircraft/707fleet.htm)

18th Sep 2002, 08:00
Tell me more about this book by Bob Ogden - I'm always looking for good reference books!


18th Sep 2002, 09:27
Bob Ogden has written a series of Museum guides for the various regions - I have three covering NE, SE and Western USA - so far as I am aware the volumes cover most parts of the world! He lists locations, opening times, plus a detailed list of all aircraft exhibited/stored by the museum.

Very useful if you are going somewhere - I picked up a copy of the Western States in the Hiller Museum at San Fran, became the bible for the rest of the trip!

You can get 'em from Amazon...

Think it is 707PA at Tamiami... wow, No 3 eh? What a shame it was scrapped.



Weight and Balance
19th Sep 2002, 05:19
Further to the story of the 720...

I was told many years ago by a Boeing employee that one of the launch customers for the 707-20 asked for a different model number, in order to stand apart from it's competitors who were already flying 707s. Thus the 707-20 became the 720, in order to close the deal.