In operation with the Turkish Government since 2016, Airbus A340-500 TC-CAN arrived in Christchurch on the evening of 17 March 2019 after a direct, 19HR 38MIN flight from the Istanbul. Operating as flight TRK4, the modified airliner has arrived in Christchurch carrying a delegation to provide support following Friday's unprecedented terrorist attack at two Muslim mosques.
It departed Christchurch just after 0400 19 March 2019 heading to Singapore and Ankara/Esenboga (LTAC/ESB).
The exceptionally long flight from Istanbul to Christchurch raised the question of "is this the longest flight to New Zealand". I believe the answer is no, however if one was to say longest flight carrying passengers then it would be yes.
However, the longest, non-stop flight to New Zealand dates back to 16 June 1993 when Airbus Industries test bed Airbus A340-200 F-WWBA dubbed "World Ranger" flew from Paris direct to Auckland in 21HR 32MIN. After 5 hours on the ground in Auckland, the A340 returned to Paris direct in 21HR 46MIN. The airliner broke six world records and had an addition five centre fuel tanks to maximise its range carrying just 22 crew and Airbus officials.