Ardern was one of a number of world leaders who will make their way to New York from London, where they attended Queen Elizabeth's funeral. The United Nations hosts "high-level week" about this time every year, when leaders from UN countries gather in New York for a week of rapid diplomacy.
About 150 leaders are expected to attend this year, which marks the first "in-person" high-level week since the pandemic.
The funeral threw the United Nations into chaos, as representatives from nearly 200 countries hastily rearranged schedules around it. The funeral has also changed the tenor of Ardern's time in New York.
She typically schedules lighthearted tourism promotion while in the city - an appearance on Stephen Colbert's Late Show, for example. All of that has been cancelled out of respect for the Queen.
The big draw of the United Nations is having so many world leaders under one roof. Arranging leader-to-leader bilateral meetings can be difficult, but it is possible to bump into a leader in the corridors and duck into a meeting room for some rapid diplomacy.
Unfortunately, Covid protocols at the United Nations building mean there is likely to be less of that this year, compared to previous years.
Ardern appears unlikely to secure a rare meeting with US President Joe Biden, although this was expected, given she has already visited him in Washington this year. Other bilateral meetings are rapidly being rearranged.
Ardern also missed the opportunity to help Air New Zealand promote its new direct flight between Auckland and New York. Ardern was meant to be on the flight and attend a flash cocktail party in New York the day after it arrived. Unfortunately for Air New Zealand, she was in London instead.
Her focus in New York is expected to be on climate change, mis- and disinformation, and online extremism.
The centrepiece of her programme is a Christchurch Call summit, which she will jointly host with French President Emmanuel Macron.
The summit will check progress made to get governments and tech companies to co-operate over efforts to root out online extremism.
Speaking to TVNZ's Breakfast from London, Ardern said the call was "making really good progress".
She'll also be filling in for Prince William at an Earthshot Prize event. Earthshot is a charity effort William founded to award grants to people who have innovative ideas for saving the planet.
Ardern will open that event with former New York City mayor Michael Bloomberg, a billionaire philanthropist.
The event is expected to draw a smattering of Hollywood celebrities.
She'll also appear on a panel discussing leadership in a pandemic. That panel will be chaired by former Prime Minister Helen Clark, who is also Ardern's former boss, and feature Ellen Johnson Sirleaf, who was President of Liberia during the Ebola crisis.
Ardern will also deliver New Zealand's statement to the United Nations General Assembly, which is a short speech highlighting topics she thinks are important to the international community this year.
Speaking to TVNZ's Breakfast before departing, Ardern said the statement would focus on "what is top of mind" for the country.
She said "nuclear disarmament" was also a big issue. Disarmament Minister Phil Twyford visited the United Nations this year for nuclear non-proliferation talks, which were ultimately vetoed by Russia in what Twyford labelled an act of "diplomatic sabotage".
Arden said she would also focus on "food security and the pandemic".
