THE SMART decision FOR THE F-35

The F135 Enhanced Engine Package (EEP): variant-common, combat-tested, coalition-assured and cost-effective. For full Block 4 capability and $40B savings over the lifecycle of the program to keep our military on the leading edge.

DESIGNED TO EVOLVE WITH THE F‑35

EEP delivers the fastest, most cost effective, lowest risk path to fully enabled Block 4 capability for all F-35 operators. 
As the air vehicle grows, so must the engine. Designed with the knowledge that operational environments evolve and threats advance, the F135’s modular design and advanced digital architecture allow for spiral development and insertion of both hardware and software – ensuring the F-35 outpaces emerging threats.

Pratt & Whitney developed EEP, a block upgrade for the F135, with the objective of providing an affordable, low risk, and agile pathway to fielding meaningful propulsion capability for all F-35 customers. EEP leverages Department of Defense investments in adaptive technology to deliver the advanced capability needed for Block 4 and beyond, while maintaining the variant-commonality and international partnership approach that the joint program was built upon. Doing so maximizes affordability for all, with EEP generating approximately $40B in lifecycle cost savings over the life of the program.

Additionally, low technical risk is a must for pilot safety on a single-engine fighter. Based on operational experience, today’s F135 is the safest fighter engine ever produced. As a derivative design, EEP builds upon the same proven architecture that has more than one million flight hours of safe and dependable operation so pilots can complete their mission and return home safely.

EEP meets the timeline and necessary requirements to support Block 4 aircraft without disrupting the program of record or driving increased cost and risk.

  • Variant-Common

    EEP is the only F-35 propulsion modernization solution that maintains variant commonality, a foundational element of the F-35 program’s design to drive economies of scale and reduce cost. As such, the F135 EEP upgrade leverages the existing production and sustainment infrastructure, and maintains the current cost share ratios with the Services and Partners. Additionally, F135 EEP is production cost neutral, retaining the sizable affordability investments that have been made to date.


    All told, F135 EEP saves the taxpayer approximately $40 billion in lifecycle costs over the life of the program, making it by far the most cost-effective modernization available for the F-35 enterprise. Those are substantial savings that can be put to use for other modernization priorities across the Department of Defense.

  • Combat Tested

    EEP upgrades an engine that is combat-tested and serving the warfighter now, powering missions for more than a dozen customers around the world. As a derivative design, EEP builds upon a proven architecture that has more than one million flight hours of safe and dependable operation between the F135 and the F119, which powers the F-22 Raptor.


    Weight neutral with a limited design scope and no air vehicle modifications required, the F135 EEP upgrade is the only true drop-in, low risk solution for the F-35.

  • Coalition-Assured

    EEP’s variant commonality strengthens the combat capability and capacity of key allies who serve as a vital pillar in U.S. national security and defense strategies at a time when geopolitical instability across the globe is increasing.


    The F135 EEP upgrade enables critical Block 4 capability for all F-35 operators, while maintaining the international partnership and alliance approach of the program -- preserving the ability to share cost and logistics over a broad enterprise to ensure F-35 interoperability and sustainability across multiple variants and users.

  • Fastest Schedule to Block 4

    As a derivative upgrade to the F135, EEP has the fastest schedule to field meaningful capability for the warfighter. Designed from the onset to be integrated into production and/or retrofit during engine overhaul, EEP leverages a production line operating at full rate, an established sustainment network and a mature supply chain. This means greater quantities of upgraded F135s and fully enabled Block 4 F-35 aircraft, sooner.


    F135 EEP leverages the Department of Defense’s investment in adaptive technology to meet the needs of Block 4 and beyond, delivering performance improvements in range, thrust, and thermal management capacity for all variants as well as powered lift for the F-35B variant. 

  • Green

    EEP supports the Department of Defense’s sustainability efforts, reducing CO2 emissions by millions of tons, saving billions in fuel costs and will be ready for sustainable fuels – just as the F135 is today.

F135 Myth Busting

Separate fact from fiction regarding the F135 engine.

Learn the facts More about the F135 F135 EEP Product Card