Originally Posted by
Vessbot
Why can't a plane be designed for the cruise condition with an exactly-level fuselage attitude (least drag) and wing incidence set for an AOA that yields best performance?
Why? Because there are numerous "cruise conditions", even on the same flight. How so? The required AOA depends on a variable that is constantly changing: weight. Do you set "best performance" for the conditions at top of climb? Half way to destination? Just before descent? With a completely full passenger load? With a partial passenger load? With full tanks? Partially filled tanks? There are multiple variables that drive weight.