The Boeing 767-400ER is one of the varients of the Boeing 767.
It is essentially a stretched Boeing 767-300ER. The "ER" bit stands
for Extended Range.
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A Boeing 767 has 3,100,000 parts.
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Boeing's website is a large repository of information of all of
Boeing's planes including the Boeing KC 135. There are also many
books about the Boeing KC 135 such as BOEING: Boeing 707 KC-135 and
Their Derivatives by Dominique Breffort available for purchase.
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Boeing 767 is what i believe you are thinking of.
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the operating empty weight of a Boeing 767-200 is
80130kilograms