Program remains on track to enable F-35 Block 4 and beyond capabilities
EAST HARTFORD, Conn., Sept. 15, 2026 /PRNewswire/ -- Pratt & Whitney, an RTX (NYSE: RTX) business, has successfully completed the F135 Engine Core Upgrade (ECU) Risk Reduction Design Review (RRDR), a major program milestone that validates the maturity of the ECU design and advances the program toward production.
The review evaluated the detailed design elements, propulsion technologies, integration considerations and risk-reduction activities critical to delivering full engine life and providing the additional power and thermal management capacity needed to support advanced sensors, weapons and other Block 4 and beyond capabilities across all three F-35 Lightning II variants. The review further assessed the industrial base's readiness to support future production and retrofit.
"Completing RRDR is an important milestone that demonstrates the maturity of the F135 Engine Core Upgrade and the progress our team is making to deliver this capability to the warfighter," said Jill Albertelli, president of Pratt & Whitney Military Engines. "As the selected propulsion modernization solution for the F-35, ECU builds on the proven F135 architecture to enable the power and thermal management needed for future capabilities, while leveraging an established global production and sustainment enterprise. This approach strengthens fleet readiness and provides operators with a proven, cost-effective path to sustain and modernize the F-35 for decades to come."
The risk reduction work, supported by the contract awarded in 2024, focuses on design maturation, aircraft integration, test preparation, supply-base readiness and related engineering activities.
"The Risk Reduction Design Review highlighted strong collaboration among our industry and government team, demonstrating a mature ECU design," said U.S. Navy Capt. Mitch Grant, F-35 Propulsion Program Manager. "The ECU program remains on track to deliver substantially improved readiness and to support F-35 modernization to outpace our adversaries."
Pratt & Whitney has delivered more than 1,500 F135 production engines to a worldwide customer base spanning 20 allied nations. The F135 Engine Core Upgrade, builds on the proven F135 architecture, maintains high commonality and is designed as a drop-in upgrade for both new-production and fielded aircraft. The ECU will be incorporated at production or retrofitted at F135 depot facilities, supporting a common, capable fleet.
About Pratt & Whitney
Pratt & Whitney, an RTX business, is a world leader in the design, manufacture and service of aircraft engines and auxiliary power units for military, commercial and civil aviation customers. Since 1925, our engineers have pioneered the development of revolutionary aircraft propulsion technologies, and today we support more than 90,000 in-service engines through our global network of maintenance, repair and overhaul facilities.
About RTX
With more than 180,000 global employees, we push the limits of technology and science to redefine how we connect and protect our world. With industry-leading capabilities, we advance aviation, engineer integrated defense systems for operational success, and develop next-generation technology solutions and manufacturing to help global customers address their most critical challenges. The company, with 2025 sales of more than $88 billion, is headquartered in Arlington, Virginia.
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