Auckland Airport · Auckland, New Zealand
First visit: 28 February 2018 · https://www.flighthistorian.com/airports/AKL
Dunedin International Airport · Dunedin, New Zealand
First visit: 23 February 2018 · https://www.flighthistorian.com/airports/DUD
At 45.92806° S, Dunedin Airport is the furthest south I’ve ever been in the world, and it’s the only airport I’ve visited to that’s closer to the south pole than the equator.
Christchurch International Airport · Christchurch, New Zealand
First visit: 23 February 2018 · https://www.flighthistorian.com/airports/CHC
Melbourne Airport · Melbourne, Victoria, Australia
First visit: 21 February 2018 · https://www.flighthistorian.com/airports/MEL
Perth Airport · Perth, Western Australia, Australia
First visit: 12 February 2018 · https://www.flighthistorian.com/airports/PER
At 11,187 miles (18,004 km) away, Perth is the furthest airport to which you can take commercial flights from DAY (and even then, only with multiple layovers).