Pratt & Whitney Awarded $2.8 Billion Contract for F135 Engines

Pratt & Whitney, a business unit of the defence contractor RTX, has been awarded an undefinitised contract action worth up to $2.8 billion (£2.08 billion/€2.41 billion) to produce the F135 engines for Lot 18 of the F-35, according to an August 26 press release. The contract provides for the production of engines for the United States and its international partners, as well as spare engines, modules, and various support services.

An undefinitised contract action (UCA) is a type of contract in which a company is authorized to begin work before all the specific terms, technical requirements, or the final price have been fully negotiated and agreed upon. This type of contract is used by governments and defence agencies when there is an urgent need for work to begin immediately and the standard, more time-consuming process of negotiating a final contract is not possible.

The F135 engine powers all three variants of the F-35: the conventional take-off and landing (CTOL) F-35A, the carrier variant (CV) F-35C, and the short take-off and vertical landing (STOVL) F-35B.

“The combat-proven F135 engine delivers the power, safety, reliability, and low-observability to ensure operators can accomplish their most critical missions,” said Christopher K. Johnson, Pratt & Whitney’s vice president for the F135 programme. “This contract will enable our team to continue providing this critical capability to help the U.S. and its allies maintain air superiority for decades to come.”

The F135 programme supports more than 67,000 domestic jobs and a network of 240 U.S. suppliers. According to the company, it contributed more than $9.1 billion (approx. £6.8 billion and €7.8 billion) to the US economy in 2024. To date, Pratt & Whitney has delivered more than 1,300 F135 production engines to a global enterprise that includes 20 allied nations.

F135 Contract History

Pratt & Whitney’s work on the F135 engine has progressed through a series of multi-billion dollar production contracts. In March 2023, the Pentagon and Pratt & Whitney finalised a deal for engine production Lots 15-17, valued at up to $8 billion. This contract covered the delivery of 278 engines for Lots 15 and 16, with an option for an additional 140 engines for Lot 17. An earlier, separate contract for Lot 17 alone was valued at $2.02 billion.

The latest award for Lot 18 continues a long-term production schedule that began with the first production contract for F135 engines in 2009. That initial contract was for long-lead hardware for six engines and was valued at $23 million, with an expected full value of up to $120 million.

Lockheed Martin is aiming for a stable production rate of 156 F-35s per year, and produced 110 in 2024 and 98 in 2023. It is expected to produce between 170 and 190 in 2025 and over 1,215 had been delivered by August 2025. The total order book covers 3,612 F-35s across the 20 participants, although those figures from Lockheed do not appear to include the UK’s recently announced intent to procure F-35As. Pratt & Whitney has delivered over 1,300 F135 engines to the F-35 global enterprise, according to the press release.

Tech Profile: F135 Engine

The Pratt & Whitney F135 is an afterburning turbofan engine designed to provide the power, stealth, and reliability required for the F-35 fighter. It is the sole engine certified for and powering all three variants of the aircraft.

Key Specifications:

• Thrust: The engine delivers up to 28,000 lbf of thrust without afterburner and up to 43,000 lbf with afterburner. This makes it one of the most powerful fighter engines in the world.
• Design: The engine features a two-spool, axial flow design and is an evolution of the F119 engine used in the F-22 Raptor. The F135 is designed with low-observable characteristics to complement the F-35’s stealth airframe.
• F-35B Variant: The engine for the F-35B short take-off and vertical landing (STOVL) variant, the F135-PW-600, includes a unique LiftSystem, which is a Rolls-Royce-produced component. This system enables the F-35B to hover, take off from short runways, and land vertically using a shaft-driven lift fan, a three-bearing swivel exhaust nozzle, and two roll posts.

Calibre comment

Support and maintenance for the F-35 is being expanded to domestic industry in several countries. Norway’s Kongsberg Aviation Maintenance Services (KAMS) established a depot in Rygge to maintain the country’s Pratt & Whitney F-135 engine that powers its fleet of 52 F-35As, for example. The Netherlands, Japan, and Australia also have domestic depots for F-35 and F135 maintenance. This may help to offset some of the immense costs associated with running and deploying the F-35. 

By Sam Cranny-Evans, published on August 27, 2025. Credit for the lead image is Pratt & Whitney.