Philadelphia Shipyard Inc., which is looking for new customers to keep its workforce employed after its last ship is completed early next year, notified the Pennsylvania Department of Labor Tuesday that it plans to layoff 275 employees by July 20.

The company, whose majority shareholder is Norwegian holding company Aker ASA, has laid off about 250 employees and contractors in recent months, reducing its workforce to 950. With the new layoffs, the workforce will drop to 675. The company has said that layoffs will continue this year as it completes work on two 850-foot-long cargo vessels, the largest container ships ever built in the United States.

The shipyard, formerly owned by the government, reopened in 1998 as a commercial company to produce large oceangoing vessels for the Jones Act market, named for the 1920 merchant-marine  measure that requires cargo shipped between U.S. ports to sail on American-made vessels.