The Pentagon on Monday awarded Lockheed Martin a $12.5 billion contract for nearly 300 of the newest F-35 Joint Strike Fighters.

The U.S. Navy said in a statement the contract modification will definitize 148 F-35s from the 18th lot of the jets and add scope for the production and delivery of another 148 fighters in lot 19.

Monday’s announcement builds on another lot 18 and 19 contract announcement from December 2024 worth $11.8 billion. It brings the total to about $24.3 billion.

Lockheed Martin will primarily build these jets at its Fort Worth, Texas, factory, and the company said it would start delivering them next year. The per-jet price increase will be less than the rate of inflation, Lockheed said.

“The F-35 Lot 18-19 contract represents continued confidence in the most affordable and capable fighter aircraft in production today,” Chauncey McIntosh, Lockheed’s vice president and general manager of the F-35 program, said in a statement. “We are proud to support our customers and further solidify the F-35’s role in enabling peace through strength.”

Twelve nations, including the United States, South Korea and Israel, now fly the more than 1,230 F-35s that are in service.

The Pentagon’s contract announcements Monday also included a $101 million cost-plus-fixed-fee deal to buy F-35 parts in advance that might face shortages or diminished manufacturing sources.

Another contract to Lockheed, worth $137 million, would pay for engineering changes to lot 17 of the F-35, as well as seek to reverse diminishing manufacturing sources.

The Pentagon also awarded Lockheed an $11.6 million contract to redesign a sensor circuit card assembly by July 2027.

Stephen Losey is the air warfare reporter for Defense News. He previously covered leadership and personnel issues at Air Force Times, and the Pentagon, special operations and air warfare at Military.com. He has traveled to the Middle East to cover U.S. Air Force operations.