>First of all, the -10 and -15 are both considered series 10 aircraft.
>Therefore, they have the same fuselage, wings and gross weights.

The DC-8-61, -62, and -63 are all series 60 DC-8s, but that does not
imply they share the same fuselage, wings, or gross weights.  They do
not!

>From what I can tell, the difference between the DC-9-14 and -15 is
that the latter has uprated engines, allowing a higher gross weight.
It's entirely possible that -14s have been upgraded to -15s, and it
appears that Northwest has done so with their fleet, but that does
not imply that *all* series 10 DC-9s have the same gross weight.

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