The aircraft that won a multi-billion dollar fight for the skies

Countries & Cities · Published 12 October 2026 Swipe more like this →

In short: Before it became the ubiquitous F-35 Lightning II, it was the X-35: a high-stakes concept demonstrator. To win the Joint Strike Fighter contract, Lockheed Martin had to prove it could master the most dangerous flight maneuver known to aviation—vertical landing—while maintaining a stealthy, multi-role profile.

The Joint Strike Fighter (JSF) program, formally contracted on November 16, 1996, aimed to replace various aging aircraft with three variants of a single design sharing over 70% of their parts. This 'commonality' was intended to slash development and operating costs. Lockheed Martin’s X-35 faced off against the Boeing X-32. The competition was won by the X-35, leading to the production of the F-35A, B, and C variants. While the X-35 was a proof-of-concept demonstrator lacking final weapon systems, it successfully reduced vertical flight risks to Technology Readiness Level 6.

The engineering of the X-35B variant was a masterclass in 'flow multiplication.' Rather than using a dedicated lift engine like the Harrier, it utilized a Pratt & Whitney F119-PW-611 turbofan. A shaft-driven lift fan, patented by Lockheed engineer Paul Bevilaqua and developed by Rolls-Royce, provided vertical thrust. This system balanced the hot core exhaust through a vectored nozzle at the tail with cool bypass air from roll-post nozzles in the wings. This configuration reduced heat damage to runways and carrier decks while allowing for a heavier takeoff payload.

The program is a massive geopolitical undertaking. The United States and United Kingdom are the primary backers, with eight other nations providing funding. Participation is tiered: the UK is a 'Level 1' partner contributing about 10% of development costs (over $2 billion), while others like Italy ($1 billion) and the Netherlands ($800 million) occupy 'Level 2.' These levels dictate technology transfer, subcontracting rights, and the priority of aircraft delivery. Despite these complexities, the F-35's introduction was delayed from 2010 to 2015 due to testing hurdles.

Significant design elements were scavenged from history. The X-35's VTOL exhaust duct drew from a 1972 Convair Model 200 requirement, and Lockheed purchased technical data from the canceled Soviet Yakovlev Yak-141 in 1991 to analyze its swivel nozzle. To transition from the X-35 demonstrator to the operational F-35, the fuselage was lengthened by 5 inches to house mission avionics, and the inlet cowl was reshaped from four-sided to three-sided to accommodate weapons bays.

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