At least 80,000 New Zealanders are overseas and not all of them will get home before flights grind to a halt, says Foreign Affairs Minister Winston Peters.
About 70,000 people are registered with the Ministry of Foreign Affairs and Trade and Peters said about another 10,000 have been making contact to lodge their whereabouts.
He said there was a narrow window to get home as the Covid-19 crisis worsens and now is the time for New Zealanders to act.
"If you're travelling it's likely you're going to be cut off shortly, so if you can get home - get home now,'' Peters said.
"We're alerting everybody we can to the fact transportations are closing up real fast, and they could be stranded there so they need to think about it hard now."
Peters said the priority was for people to use commercial flights while these were still available, but in work on alternative plans was underway, including the use of charter planes.
- If you have symptoms of the coronavirus, call the NZ Covid-19 Healthline on 0800 358 5453 (+64 9 358 5453 for international SIMs)
He said he could not put a number on how many New Zealanders may not get home in the current window, but every option was being considered for those who got stranded.
Prime Minister Jacinda Ardern also wanted it was not a time for panic, but "a time for preparation''.
"We need New Zealanders to prepare - think about Covid-19 in the same way you do for civil defence emergencies.
"Prepare a plan for you and your family, think about what you'll do in situations where you might need to work from home, think about what you'll do in a situation where your family might need to self-isolate,'' she said.
Ardern is also advising all people who returned to New Zealand in the past 14 days to quarantine.
"If you arrived before those border restrictions, seeing out the balance of your 14 days in self isolation is the sensible, safest and best thing you can do for your community around you."
Ardern said some of the eight new people to test positive for Covid-19 had arrived back before the new border controls kicked in, which is why she's encouraging people who have come home in the last two weeks to self-isolate.
On Monday an effective ban on mass gatherings of 500 people or more was announced.
Ardern is planning to provide more advice and guidance on mass gatherings - potentially limiting crowds even more - and that announcement is expected in the next 24 hours.
The Ministry of Foreign Affairs and Trade is also calling home some of its staff on placements overseas.
Peters said all staff are being asked if they want to come home and others are being fast-tracked, particularly where New Zealanders have underlying health issues.
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