An Air Force F-35 Lightning II Demonstration Team aircraft takes off from Tinker Air Force Base, Oklahoma on 25 May 2021. The team visited the Oklahoma City Air Logistics Complex’s Heavy Maintenance Center to thank the men and women for their work on sustaining the F135 engine, which powers the F-35A. Credit: DVIDS.

The US Department of Defense (DoD) has made an effort to ensure a timeline for upgrading the sophisticated F135 engine that powers the F-35 Lightning II fighter jet.

It has allocated “full funding” worth $497m to the F135 Engine Core Upgrade, also known as the Block 4 programme, as part of the recent Defense Appropriations Bill for fiscal year 2024.

Go deeper with GlobalData

Data Insights

The gold standard of business intelligence.

Find out more

Related Company Profiles

View all

According to concerns repeatedly voiced by the US Government Accountability Office in two reports published in 2023, the engine was originally due to be completed in 2026 and determined to cost $10.6bn. However, this ‘Block 4’ upgrade has risen to $16.5bn and now estimated to conclude in 2029.

Ultimately, Block 4 addresses new threats to the aircraft since the DoD’s original requirements more than two decades ago. Block 4 capabilities require more power and cooling than anticipated, which has prompted the DoD to modernise the overworked F135 engine.

As a result of new demands in a different technological era, the DoD has added extra capabilities nearly every year since Block 4 began – leading to the aircraft’s capabilities growing from 66 to 80.

Fundamentally, the problem with the modernisation programme is that the DoD has not been able to distinguish its higher-than-expected costs, leaving the US Congress with “no clear picture of why demands and costs have spiked.”

How well do you really know your competitors?

Access the most comprehensive Company Profiles on the market, powered by GlobalData. Save hours of research. Gain competitive edge.

Company Profile – free sample

Thank you!

Your download email will arrive shortly

Not ready to buy yet? Download a free sample

We are confident about the unique quality of our Company Profiles. However, we want you to make the most beneficial decision for your business, so we offer a free sample that you can download by submitting the below form

By GlobalData
Visit our Privacy Policy for more information about our services, how we may use, process and share your personal data, including information of your rights in respect of your personal data and how you can unsubscribe from future marketing communications. Our services are intended for corporate subscribers and you warrant that the email address submitted is your corporate email address.

Pratt & Whitney won a contract to undertake an F135 upgrade study and operational assessment by the F-35 Joint Program Office to identify propulsion system growth needs for Block 4.2 F-35 aircraft and above in October 2020.

“We are thankful that Congress has embraced and enacted the Defense Department’s decision to upgrade the F135 with the Engine Core Upgrade, the lowest-risk, most cost-effective solution to modernizing the F-35,” said Jeff Shockey, senior vice president, RTX government relations.

“We are fortunate to enjoy continued bipartisan and bicameral support and leadership from our congressional advocates on this critical capability for the warfighter; particularly Sen. Susan Collins, Rep. Rosa DeLauro, and many other members that continue to be staunch advocates of the F135 programme.”

The legislation also includes continued support for the Next-Generation Adaptive Propulsion programme, a portion of which will be provided for Pratt & Whitney’s XA103 adaptive engine to continue moving toward detailed design review for the prototype engine.