The Pentagon’s Lot 18 deal with Pratt & Whitney sets F135 engine cost at $20m, up from $14–15m in Lot 17, pushing Lockheed Martin F-35A unit price past $100m.
The Pentagon's most recent Lot 18 agreement with Pratt & Whitney has raised the F-35A's flyaway cost back beyond $100 million. Each F135 engine now costs an average of $20 million, up from Lot 17's $14–15 million.
The U.S. Department of Defence has given Pratt & Whitney (RTX) a $2.8 billion deal for 141 F135 engines, which works out to around $20 million per engine.
This represents a significant increase compared to Lot 17, where the engine price was closer to $14–15m, and has lifted the F-35A’s unit cost to more than $100m.
Unlike the aircraft flyaway cost, which bundles the airframe, a single engine and baseline systems, engine contracts often include extra modules, tooling and spares, inflating per-engine calculations. Rising input costs and broader contract scope also contribute to the increase.
The need for greater power and cooling produced by Technology Refresh 3 and the impending Block 4 upgrade is a big part of this. In 2023, the Pentagon chose the Engine Core Upgrade (ECU) approach to address these demands. This improved the F135 instead of paying for a brand-new engine.
These upgrades bring additional development and integration expenses that are already shaping production lots.
In short, Lot 18’s $20m price tag per F135 should not be viewed as a peak. As ECU modifications and Block 4 capabilities are implemented, both the engine and the fighter’s total cost are expected to rise further in upcoming lots.
