You míst agin by not adding the cargo load, which typically can be 10-20 ton or limited by performance/structural weight
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Also, there are 3 engine types available for the 330 with 3 different cruise profiles (RR,GE and PW in descending order). Which type was on this aircraft?
And what was the actual SAT profile (may be quite off ISA in the area). Changes max alt if above ISA+10/15.
The book values given to you are no-wind. Small variations in entered FMS winds can change optimum level vs weight by several thousand feet.
Furthermore, on the South Atlantic run one may prefer to step early while still in VHF contact and to negotiate CBs above the cell layer (giving you slightly more space between the stakes in the fence). However, the reduction in maneuvre margin makes this decision slightly delicate.
Just a few of several variable....I suppose one reason why long haul pilots generally are paid better than ....e.g. journalists??
Stop speculating...
Turbo