Pratt & Whitney, part of RTX, has received a contract modification worth $3.8bn for the production of lots 18 and 19 of the F135 engine.

The engine powers all three models of the F-35 Lightning II, which recently exceeded one million engine flight hours.

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According to RTX, the latest modification finalises production for lot 18 and supports the manufacturing of propulsion systems for lot 19 F-35 aircraft.

The aggregate value of the lots 18-19 contracts awarded to Pratt & Whitney totals $6.6bn.

The agreement covers full-rate production engines, initial spare parts, modules, engineering resources, programme oversight and dedicated production support services. It also addresses capacity requirements, tooling and ensures continuous manufacturing and supply chain operations for both domestic military branches and international partners.

Pratt & Whitney military engines president Jill Albertelli said: “The F135 is the most advanced military engine in the world, delivering unmatched thrust, reliability and mission readiness for the US and its allies.

“Pratt & Whitney is investing heavily across our global production base and supply chain to increase production and accelerate engine delivery and sustainment to meet growing global demand for the F-35 programme.”

The RTX subsidiary has invested more than $1bn over the past five years to expand and modernise its global production facilities. This has led to a 20% increase in F135 engine production rates compared to earlier contract levels.

Overall, the F135 programme supports more than 66,000 jobs across 47 states and territories in the US, generating over $9bn in domestic economic impact in 2025.

More than 1,400 F135 engines have been delivered for use in the F-35 programme, which includes participation from 20 allied nations.

In December last year, Pratt & Whitney secured an undefinitised contract action valued at $1.6bn for sustainment services related to F135 engines. The F135 engine provides more than 40,000 pounds of thrust.