Lockheed Martin will add 400 workers to boost production of the F-35 fighter jet, the most expensive in U.S. history, after making a good on an earlier promise to President Trump to increase the aircraft’s workforce by 1,800.

“The F-35 is an iconic product,” Lockheed Chief Executive Officer Marillyn Hewson said in a statement. “The program supports 194,000 direct and indirect jobs nationwide, and as we ramp up production we are creating even more opportunities for American workers.”