The F135 engines are for F-35 Lightning II aircraft, the company said, and the modification for more of them is worth $508 million, which brings the total value of sixth lot production to $1.1 billion.
The low-rate initial production contract, or LRIP, is for 38 engines, as well as program management, engineering support, sustainment and spare parts. The 38 total engines in the LRIP 6 contract include 36 install engines and two conventional takeoff and landing spare engines.
Pratt & Whitney said the U.S. Air Force will receive 18 conventional takeoff and landing engines, while the U.S. Navy will receive seven carrier variant engines. The U.S. Marine Corps will receive 6 short takeoff and vertical landing engines.
The sixth lot contract also includes three engines for Italy's F-35s and two for Australia.
The price for the 32 common configuration engines -- used to power both the conventional takeoff and landing aircraft variant and the carrier variant -- has been reduced 2.5 percent in sixth lot production compared to the price for 35 engines in fifth lot production.
The decrease in price for the six short takeoff and vertical landing systems is about 9.6 percent less for the three produced in the fifth lot.
"Increasing the volume and production rate for F135 engines will be critical to realizing further cost savings for the propulsion system," said Chris Flynn, vice president, Pratt & Whitney F135/F119 engine programs. "We remain focused on reducing costs, meeting our delivery schedule commitments, and increasing the tempo of contracting for LRIP 7 and LRIP 8.
"As the fleet is expanding, Pratt & Whitney is equally committed to driving down long-term sustainment costs."
Pratt & Whitney has delivered 115 production engines so far. Deliveries of sixth lot production engines begin this year.