ATSB Pel-Air report excluded critical fuel factor | Plane Talking
No RVSM!!!
This raises a plausible explanation for not taking full fuel. He had to get to FL390 soon after departure, and he had 6 POB. Could a WW do this with full fuel? Or did he need to go light on the fuel to comply?.
When told to descend from 350 to 270 he instead requested 390 due fuel consumption.
The alternative presumably would have been to plan full fuel and cruise below RVSM, with a higher fuel cost.