I've been trying hard to keep away from this, but I can't let this one go
Also extra fuel usage means less reserves- wait for a repeat of Norfolk Island accident where the aircraft was held low because it could not get a RVSM dispensation.
The flight departed Samoa at 0545, and initially climbed to flight level 350 (FL350) in airspace that was controlled from New Zealand. High frequency (HF) radio was used for long distance radio communication between the aircraft and air traffic control (ATC) and very high frequency (VHF) radio for line of sight radio communications with airport service providers.
At 0628, when the aircraft was approaching the intended cruising level of FL350, ATC instructed the flight crew to descend to FL270 by time 0650 in order to maintain separation with crossing traffic. The flight crew later reported to ATC that a descent to that altitude would have increased the aircraft’s fuel consumption and requested a climb to a higher flight level. At 0633, ATC issued an amended clearance for the flight crew to climb to FL390 and the aircraft was established at this level at 0644.The flight continued at FL390 until the descent into Norfolk Island.