The STB now has 30 days to decide whether the application is complete; a formal review by the regulator would likely stretch for more than a year and include public hearings.
The carrier and ports group said revenue on all major trades, except its domestic network, fell in the first quarter, resulting in a 13% drop in revenue from container shipping.
The Cosco subsidiary said the 13,600-TEU ships have been ordered from Shanghai-based shipyard Hudong-Zhonghua Shipbuilding for delivery between 2028 and 2030.