Passengers were baffled and angered today when Jetstar cancelled flights due to fog, despite clear skies and Air New Zealand flights departing on time.
Jetstar services between 6am and 8am from Auckland to Wellington and return, and Auckland-Christchurch return were cancelled yesterday evening.
When the fog cited by Jetstar as the reason for the cancellations had gone by morning, would-be passengers expressed confusion via social media.
Student Nicole Botherway tweeted: "Air nz is flying... Jeez stop being stupid jetstar [sic]".
Jetstar spokesman Phil Boeyen said "several hundred Jetstar customers would have been affected by this morning's fog but we expect to have all flights back on track by later today".
But Air New Zealand at the same time had "no significant delays or cancellations'' to services between Auckland and Wellington.
One Christchurch-Queenstown return service was cancelled due to fog at Queenstown Airport, spokesman Andrew Aitken said.
Neither Auckland nor Wellington were affected by heavy fog today, MetService meteorologist Dan Corbett told Fairfax Media.
Hamilton and Dunedin were as was - to a lesser extent - Christchurch.
Airlines made their own decisions based on weather forecasts, which were regularly updated, he said.
"[Airlines} are getting their information continuously," Corbett said. "Conditions from what I see didn't look too bad."
Fog was "patchy" over Auckland and "lower in the early hours of the morning" but not heavy.
Jetstar delayed overnight trans-Tasman flights to avoid the fog, which resulted in the cancellation of early morning domestic flights, Boeyen said.
"All airlines run differently and have different network planning around the aircraft," he said.
"Rather than delaying flights and being behind schedule all day, we might instead cancel one flight and put those passengers onto another aircraft.
"It's not about saving money, we do it to avoid disruption."
All affected passengers were informed of the cancellation yesterday evening, and were rebooked onto other Jetstar services today.
Jetstar in April announced cancellation of 300 Jetstar flights during May and June, with most of the cuts on the Auckland-Wellington route, due to low seasonal demand.