New Zealand's KiwiRail is eyeing up newbuildings to replace ageing Interislander ferries.

Three elderly ships will get the chop, with two new vessels coming into service by 2024.

The vessels facing the axe are the 360-pax Aratere (built 1998), the 1,650-pax Kaitaki (built 1995) and the 252-pax Kaiarahi (built 1998).

KiwiRail acting chief executive Todd Moyle told Stuff: "Two new ferries will carry more freight, cars and passengers than the previous fleet which had a mix of rail ships, and ships that carried rail freight on wagons.