Lockheed Martin has been awarded a $450 million modification to a previous contract to develop F-35 fighter jets for South Korea, the Pentagon announced in a statement Thursday.

“This modification continues the integration work to implement the development and delivery of the F-35A Air System to the Republic of Korea under the Foreign Military Sales program,” the statement said. “This effort will also provide for non-recurring engineering work.”

The work will be completed in Fort Worth, Texas, and is expected to be finished by August 2019, according to the Pentagon.

The modification adds nearly 50 percent to the original $920 million contract awarded to Lockheed Martin in 2015.

ADVERTISEMENT

The contract was for 78 F-35As for the U.S. Air Force, Italy, Turkey, Australia, Norway and various foreign military sales customers; 14 F-35Bs for the Marine Corps, Britain and Italy; and two F-35Cs for the Navy and Marines.

In the foreign military sales program, the Pentagon facilitates sales between contractors and foreign governments.

The F-35 program has lately come under repeated fire from President-elect Donald Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE, who has blasted what he says are out-of-control costs.

It’s also been criticized in the past by some members of Congress for repeatedly going over the budgeted cost and time for projects.

Defenders of the program say issues were in the research and development phase. Now that the planes are in production, they say, the price per unit is going down.

Supporters also highlight that other countries have purchased the jet and argue that there is currently no alternative to the F-35, which is meant to replace Cold War-era fighter jets.

The program is estimated to cost a total of $400 billion for 2,457 planes.