Lockheed Martin said Friday that it had hired 300 temporary workers to replace striking union employees at its fighter plane plant in Fort Worth and could hire hundreds more.

About 3,300 union workers went on strike there on April 23 over proposed changes in health benefits and a Lockheed plan to stop offering a traditional pension to newly hired workers.

The factory builds the new F-35 strike fighter aircraft as well as an older model, the F-16, for foreign countries. The company has used salaried workers to keep building the planes at a slower rate. It started bringing in the temporary workers in late May.

Joe Stout, a Lockheed spokesman, said the company would continue hiring substitutes and could bring in up to 2,000 if the strike continued through the summer.