Seaspan Corp is breaking new ground with an order for its largest containerships to date.

The company has inked a contract with a major shipyard for two 24,000-teu boxships to be delivered in the first half of 2023.

The orders are placed on the back of an 18-year charter with an unnamed liner operator.

Seaspan, a subsidiary of New York Stock Exchange-listed Atlas Corp, said the two newbuildings will have conventional fuel systems, but will include emissions reduction technologies.