LAN but book under the QF code if you can, but that is if you want to earn QFF.
If you want to earn VFF points, go with AirNZ, put in your SQ KF # and earn there, and then transfer the points to VFF, of course, you will not be able to transfer status tho.
Yes, just checked, for AirNZ flights from NZ to South Am, you have to go via the US.
Checked on the AirNZ website, to EZE (Buenos Aires), it transits in IAH, where you will get Y from IAH to EZE, so would be the same doing the opposite.
Edit: looks like as of now, AirNZ has not resumed flights to South Am, so maybe for that, have to go via the US.
AirNZ and VFF broke up a few years back.
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Doing long haul like that, esp one way in J is very expensive.
Expect to pay in the range of at least Aud$10,000.
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Seeing that VFF has joined UAL, if you want status, and VFF, maybe go with them from South Am to the US, to transit then to Aust.
Need an ESTA tho.
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LIM to IAH, to SYD, ignoring AirNZ code share, UA is asking, for Jan 10, 2024, Usd$11242 (one way), as seen on the UA website.
This will earn you VFF points and VFF SC.
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Sorry for the waffly.