Latetonite,
Think about the days without FMC's and VNAV.
My aircraft is fitted with 2 Fmc and vnav.
At the point you will need MCT to maintain cruise altitude, you reached your maximum altitude for that speed.
As this is not an advisable operating, you fly lower.
Exactly so do you routinely need MCT?
Based on margin calculated, you will get a lower, Normal, 'max' Cruise setting, below the engines will operate for given weight, speed and ambient conditions.
This setting will also prevent the thrust levers going "al the way"( to what?), just to adapt for normal speed deviations, in which there is in fact no "hurry".
Exactly...and what happens when the thrust is kept to a lower max?
Just a guess: it's just about economics. Most of the time, you don't need MCT, so if Boeing says 94.6% is the limit, the engine/airframe will be that much more "fuel efficient." That 0.00001% of cruise at MCT costs more fuel. When marketing is digging for every dime, they can sell a less expensive CASM than the other guys.
Oups ...seems like Crunk nailed it.
