The Interislander is putting on additional sailings of the Aratere tonight and tomorrow to help people get home for the nationwide alert level 4 lockdown.
Prime Minister Jacinda Ardern announced this afternoon the grace period for air travel from Queenstown and the Cook Strait ferry had been extended for 24 hours.
"This applies only to people needing to return home and is in response to the large amount of demand that we have on those facilities."
Interislander executive general manager Walter Rushbrook said the additional sailings were to provide extra capacity for homeward travel until 11.59pm on Friday.
The Kaiarahi would stay on its normal schedule at this stage, and passenger bookings were now open for tomorrow's sailings, he said.
People have been asked to visit the Interislander's website or ring its call centre to make bookings.
Only people travelling to their home should make bookings and proof of address is required at check in.
"We expect demand for bookings to increase and there is limited time for people to get home, so it is crucial that only those who have a valid reason for travelling make bookings", Rushbrook said.
Covid-19 risk mitigations have been put in place at terminals and on the ships, including wearing PPE, providing 2m distance markers, restricting food and beverage services and heightened cleaning regimes.
Rushbrook acknowledged it was a challenging time.
"After the period for travel home ends at 11.59pm tomorrow, and if we are still at level 4, members of the public will not be allowed to travel on the ferries unless they are essential workers or have a valid reason for travel, as permitted by the Ministry of Health."