No clear date for when the Interislander's Kaitaki will be back on the sea, after being out of order since March 6.

Interislander passengers with trips planned in early April have been told their sailing is off.

It'll be at least April 10 before the Kaitaki's crossing Cook Strait again.

Executive General Manager Walter Rushbrook says meanwhile, they're doing all they can.

That includes adding some Easter weekend sailings.

"We're looking to make sure that we provide certainty that they know the status of their booking, and get across Cook Strait as soon as possible. And as soon as we know when Kaitaki's going to be back in service, we'll open up our booking system fully again."

LISTEN ABOVE

• Interislander ferry to resume passenger sailings after mayday
• Interislander ferry turns back after medical event on board
• Interislander's Kaitaki ferry facing more issues, taken out of service
• Would-be Cook Strait ferry passenger on Interislander's lack of communication