The Lockheed Martin F-35 Lightning II is an American family of single-seat, single-engine, supersonic stealth strike fighters. A multirole combat aircraft designed for air superiority and strike missions, it also has electronic warfare and intelligence, surveillance, and reconnaissance capabilities. Lockheed Martin is the prime contractor, with partners Northrop Grumman and BAE Systems. The aircraft has three main variants: the conventional takeoff and landing F-35A, the short take-off and vertical-landing F-35B, and the catapult-assisted take-off but arrested recovery F-35C. With 883 aircraft in service , it is the world's fourth-most-numerous military aircraft, and most-numerous stealth aircraft.

The aircraft descends from the Lockheed Martin X-35, which in 2001 beat the Boeing X-32 to win the Joint Strike Fighter program, to replace the F-16 Fighting Falcon, F/A-18 Hornet, the McDonnell Douglas AV-8B Harrier II, and others. Development was primarily funded by the United States, with additional funding from select NATO members and Australia; Turkey was removed from the program in 2019. , the US operates all three main variants; both F-35As and F-35Bs are operated by Italy and Japan; F-35As are operated by Australia, Belgium, Denmark, Netherlands, Norway, Poland, and South Korea; and F-35Bs are operated by the United Kingdom. Israel operates its own F-35I variant. Six further NATO members, as well as Switzerland and Singapore, have also placed orders, and other countries are considering purchases.

The program has drawn criticism for its unprecedented size, complexity, ballooning costs, and delayed deliveries, partially caused by low rate initial production during its development. , the program is expected to cost US$2 trillion through 2088, about half of which is due to inflation. The unit flyaway costs of the 296 aircraft in lots 18-19, for which deliveries start in 2026, are $92M for the F-35A, $121.4M for the F-35B, and $110.8M for the F-35C (2026 dollars). Flyaway costs include all the basic marginal costs to produce one aircraft, including the government-furnished jet engines and radars. The F135 engine contributes $20.4 million to this flyaway cost

The F-35 first flew in 2006; its variants entered US service in 2015 (Marine Corps F-35B), 2016 (Air Force F-35A), and 2019 (Navy F-35C). The F-35 first saw combat in the 2018 Israeli strikes in Syria, the F-35B in 2018 by US strikes in Afghanistan, and the F-35C in 2024 in US strikes in Yemen. F-35s have since been used in combat by the US in Iraq, Iran (2025 and 2026), and Venezuela; by Israel in Gaza, Iraq, Iran (2025 and 2026), Lebanon, and Yemen; and by the UK in Iraq and Syria; F-35As can deliver two US B61 nuclear bombs, including those deployed in the Netherlands and the United Kingdom. Belgium, Germany, Italy, and the UK plan to buy nuclear-capable F-35As. The US plans to buy 2,456 F-35s through 2044, which will represent the bulk of its crewed fixed-wing tactical aviation for several decades; the aircraft is to be a cornerstone of NATO and US-allied air power and operate until 2088.

Development

Program origins The F-35 was the product of the Joint Strike Fighter (JSF) program, which was the merger of various combat aircraft programs from the 1980s and 1990s. One progenitor program was the Defense Advanced Research Projects Agency (DARPA) Advanced Short Take-Off/Vertical Landing (ASTOVL), which ran from 1983 to 1994; ASTOVL aimed to develop a Harrier jump jet replacement for the US Marine Corps (USMC) and the UK Royal Navy. Under one of ASTOVL's classified programs, the Supersonic STOVL Fighter (SSF), Lockheed's Skunk Works conducted research for a stealthy supersonic STOVL fighter intended for both US Air Force (USAF) and USMC; among key STOVL technologies explored was the shaft-driven lift fan (SDLF) system. Lockheed's concept was a single-engine canard delta aircraft weighing about empty. ASTOVL was rechristened as the Common Affordable Lightweight Fighter (CALF) in 1993 and involved Lockheed, McDonnell Douglas, and Boeing.

The end of the Cold War and the collapse of the Soviet Union in 1991 caused considerable reductions in Department of Defense (DoD) spending and subsequent restructuring. In 1993, the Joint Advanced Strike Technology (JAST) program emerged following the cancellation of the USAF's Multi-Role Fighter (MRF) and US Navy's (USN) Advanced Attack/Fighter (A/F-X) programs. MRF, a program for a relatively affordable F-16 Fighting Falcon replacement, was scaled back and delayed due to post–Cold War defense posture easing F-16 fleet usage and thus extending its service life as well as increasing budget pressure from the Lockheed Martin F-22 Advanced Tactical Fighter (ATF) program. The A/F-X, initially known as the Advanced-Attack (A-X), began in 1991 as the USN's follow-on to the Advanced Tactical Aircraft (ATA) program for a Grumman A-6 Intruder replacement; the ATA's resulting McDonnell Douglas A-12 Avenger II had been canceled due to technical problems and cost overruns in 1991. In the same year, the termination of the Naval Advanced Tactical Fighter (NATF), a naval development of USAF's ATF program to replace the Grumman F-14 Tomcat, resulted in additional fighter capability being added to A-X, which was then renamed A/F-X. Amid increased budget pressure, the DoD's Bottom-Up Review (BUR) in September 1993 announced MRF's and A/F-X's cancellations, with applicable experience brought to the emerging JAST program. JAST was not meant to develop a new aircraft, but rather to develop requirements, mature technologies, and demonstrate concepts for advanced strike warfare.

As JAST progressed, the need for concept demonstrator aircraft by 1996 emerged, which would coincide with the full-scale flight demonstrator phase of ASTOVL/CALF. Because the ASTOVL/CALF concept appeared to align with the JAST charter, the two programs were eventually merged in 1994 under the JAST name, with the program now serving the USAF, USMC, and USN. JAST was subsequently renamed to Joint Strike Fighter (JSF) in 1995, with STOVL submissions by McDonnell Douglas, Northrop Grumman, Lockheed Martin, and Boeing. The JSF was expected to eventually replace large numbers of multi-role and strike fighters in the inventories of the US and its allies, including the Harrier, F-16, F/A-18, Fairchild A-10 Thunderbolt II, and Lockheed F-117 Nighthawk.

International participation is a key aspect of the JSF program, starting with United Kingdom participation in the ASTOVL program. Many international partners requiring modernization of their air forces were interested in the JSF. The United Kingdom joined JAST/JSF as a founding member in 1995 and thus became the only Tier 1 partner of the JSF program; Italy, the Netherlands, Denmark, Norway, Canada, Australia, and Turkey joined the program during the Concept Demonstration Phase (CDP), with Italy and the Netherlands being Tier 2 partners and the rest Tier 3. Consequently, the aircraft was developed in cooperation with international partners and available for export.

JSF competition

Boeing and Lockheed Martin were selected in early 1997 for CDP, with their concept demonstrator aircraft designated X-32 and X-35, respectively; the McDonnell Douglas team was eliminated, and Northrop Grumman and British Aerospace joined the Lockheed Martin team. Each firm would produce two prototype air vehicles to demonstrate conventional takeoff and landing (CTOL), carrier takeoff and landing (CV), and STOVL. Lockheed Martin's design would make use of the work on the SDLF system conducted under the ASTOVL/CALF program. The key aspect of the X-35 that enabled STOVL operation, the SDLF system consists of the lift fan in the forward center fuselage that could be activated by engaging a clutch that connects the driveshaft to the turbines and thus augmenting the thrust from the engine's swivel nozzle. Research from prior aircraft incorporating similar systems, such as the Convair Model 200, Rockwell XFV-12, and Yakovlev Yak-141, was also taken into consideration. By contrast, Boeing's X-32 employed a direct lift system that the augmented turbofan would be reconfigured to when engaging in STOVL operation.

Lockheed Martin's commonality strategy was to replace the STOVL variant's SDLF with a fuel tank and the aft swivel nozzle with a two-dimensional thrust vectoring nozzle for the CTOL variant. STOVL operation is made possible through a patented shaft-driven LiftFan propulsion system. This would enable an identical aerodynamic configuration for the STOVL and CTOL variants, while the CV variant would have an enlarged wing to reduce landing speed for carrier recovery. Due to aerodynamic characteristics and carrier recovery requirements from the JAST merger, the design configuration settled on a conventional tail compared to the canard delta design from the ASTOVL/CALF; notably, the conventional tail configuration offers much lower risk for carrier recovery compared to the ASTOVL/CALF canard configuration, which was designed without carrier compatibility in mind. This enabled greater commonality between all three variants, as the commonality goal was important at this design stage. Lockheed Martin's prototypes would consist of the X-35A for demonstrating CTOL before converting it to the X-35B for STOVL demonstration and the larger-winged X-35C for CV compatibility demonstration.

The X-35A first flew on 24 October 2000 and conducted flight tests for subsonic and supersonic flying qualities, handling, range, and maneuver performance. After 28 flights, the aircraft was then converted into the X-35B for STOVL testing, with key changes including the addition of the SDLF, the three-bearing swivel module (3BSM), and roll-control ducts. The X-35B would successfully demonstrate the SDLF system by performing stable hover, vertical landing, and short takeoff in less than . The X-35C first flew on 16 December 2000 and conducted field landing carrier practice tests.

On 26 October 2001, Lockheed Martin was declared the winner and was awarded the System Development and Demonstration (SDD) contract; Pratt & Whitney was separately awarded a development contract for the F135 engine for the JSF. The F-35 designation, which was out of sequence with standard DoD numbering, was allegedly determined on the spot by program manager Major General Mike Hough; this came as a surprise even to Lockheed Martin, which had expected the F-24 designation for the JSF.

Design and production

As the JSF program moved into the System Development and Demonstration phase, the X-35 demonstrator design was modified to create the F-35 combat aircraft. The forward fuselage was lengthened by to make room for mission avionics, while the horizontal stabilizers were moved aft to retain balance and control. The diverterless supersonic inlet changed from a four-sided to a three-sided cowl shape and was moved aft. The fuselage section was fuller, the top surface raised by along the centerline and the lower surface bulged to accommodate weapons bays. Following the designation of the X-35 prototypes, the three variants were designated F-35A (CTOL), F-35B (STOVL), and F-35C (CV), all with a design service life of 8,000 hours. Prime contractor Lockheed Martin performs overall systems integration and final assembly and checkout (FACO) at Air Force Plant 4 in Fort Worth, Texas, while Northrop Grumman and BAE Systems supply components for mission systems and airframe.Keijsper 2007, pp. 122, 124.