RTX subsidiary Pratt & Whitney has completed a key design review for its F135 Engine Core Upgrade (ECU), advancing the program toward production and eventual integration with the F-35 fleet.
The Risk Reduction Design Review examined the ECU’s detailed design, propulsion technologies, aircraft integration, test preparations, and supply chain readiness. The company said the review validated the maturity of the design and assessed preparations for future production and retrofits.
Work on the risk-reduction phase began under a contract awarded in 2024. The effort covers design maturation, aircraft integration, test preparation, supply-base readiness, and related engineering activities.
For the F-35, the ECU is designed to provide additional power and thermal management capacity needed for advanced sensors, weapons, and other capabilities planned under the aircraft’s Block 4 modernization program.
“The ECU program remains on track to deliver substantially improved readiness and to support F-35 modernization to outpace our adversaries,” F-35 program manager US Navy Captain Mitch Grant said.
The company has delivered more than 1,500 F135 production engines to customers across 20 allied nations.
F135 Upgrades
The F135 powers all three F-35 variants: the conventional takeoff and landing F-35A, the short-takeoff and vertical-landing F-35B, and the carrier-capable F-35C.
In August, Pratt & Whitney secured a nearly $1.3-billion contract for F135 engine spare parts and support equipment for US and allied F-35 fleets. The award covers replacement components, deployable spares, depot inventory, and related equipment.
In April, the Pentagon awarded Pratt & Whitney $3.8 billion to produce F135 engines for the F-35, including Lot 18 and additional Lot 19 production.
Earlier, in December 2025, the US Navy awarded Pratt & Whitney $1.6 billion for F135 sustainment, covering spare parts, technical support, propulsion integration, and training.
