I'll update my comment:--
The idea in any Jet is to achieve the best kg/gnm. The company will hopefully provide a flight plan to achieve this aim, you may need to modify your levels/speeds to actually achieve or better it on the flight, it is up to you
AND ATC to work it out. If .63 at FL240 below the wind is best then
I dont think any Airline manager would disagree as long as reduced fuel burn was achieved.
That's why they pay us the big bucks, oops did I just say that
