as the never realized 707-700 engines upgrade debacle showed all too well
Eh?
So the 707/C-135s with CFM engines were upgraded by a 3rd party company...
Well, I don't know.

I was talking about the never happened Boeing's upgrade on demand of the then still new 707's to CFM56 engines. Thing studied on the last 707-300 built (that was later re-engined normal JT3D and then sold to Morocco's army) and then rejected by Boeing (mainly because it would have eroded potential buyers to the then new 757), back in the 80ies.

As already stated, Douglas was WAY better.

If a working 707 was ever upgraded to CFM56 engines (thing that I honestly ignore), it was without Boeing's help nor approval.
BTW, if a thing like that ever happened, could you give me more details, or even a link perhaps? Quite interested here. :-?




