Re: What's in a model number? (MD-95 Structural Specs)

From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
Date:         21 Nov 95 01:19:27 
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> These MODEL numbers you are quoting are in fact airline designators.

They're still part of the official model designation of the aircraft
as listed on the aircraft's FAA certificate.

> Boeing designates the 2 digit number following the model to
> individual airlines.

Yup.  A reasonably full list (~250 of them) is available from the group's
archives (

> The differences are not only in the engines (which are the same in the above
> examples) but in the general options selected and layouts in the aircraft.
> No two airlines select exactly the same equipment and cabin layouts for their
> aircraft so the differences are noted in the "customer" number

Airlines can and do pool orders together, with common specs, to save
money or get quicker delivery.  For example, Delta's five DC-10s were
built to United specs.  (I can't think of any good Boeing examples
offhand, though they no doubt exist.)

At the other end of the spectrum, United has a pair of 747-451s.  They
are identical to a 747-422 save designation, and rather different from
all the 747-451s owned by Northwest.  Why aren't they -422s?  (They
were built for Northwest but cancelled before delivery and retrofitted
to UA specs.  Though rare, there are similar examples in which Boeing
*did* change the designation prior to delivery.)

Consider, too, the 707-138.  Not only does it have different engines
than other (or at least earlier) 707-100s, it's about ten feet shorter!
That's a pretty major customer option!

Karl Swartz	|Home
Moderator of sci.aeronautics.airliners -- Unix/network work pays the bills