"Kiltrash"
There are no alternative airports on this route.
Every time I fly back to Sydney on QF18 I hope the headwinds arn't to bad as sometimes the plane gets down to below 450mph and the pilots keep heading south to find less headwind. I believe that if anything happened in the middle of the flight like loss of an engine the only diversion would be Christchurch or Auckland if you were lucky and some flights do land in Auckland on the way back to take on extra fuel.
It s definately one of the most dangerous flights in the world but if the winds are against you the flight over Antarctica is definately worth the risk in the best 747-400's ever built.
