The Aratere ferry will be back sailing tonight, three days after a minor mechanical failure was discovered.
"The Aratere sails Cook Strait 19 hours a day, five days a week," Kiwirail chief executive Peter Reidy said.
"It's a real workhorse for the country, extending SH1 across the sea for our people and our freight.
"In the year to June 30, Aratere missed only two return sailings due to engineering issues out of approximately 900 return sailings."
Kiwirail's use of two other ferries - the Kaitaki and Kaiarahi, which was brought back into service to replace the Aratere - meant the backlog of passengers and freight following three days of storm last week was now mostly cleared.