Also check AKL-SCL availability -- sometimes it is different than SYD-SCL. Though it would be pretty wierd to fly SYD-SCL in L with empty F seats and then AKL-SCL in A on the same plane -- but it can happen. Otherwise your only other option would be to fly SYD-PPT on a separate ticket and then PPT-SCL on LA (which does count as a pacific ocean crossing).