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Unlocking Sixth-Gen Air Power: Inside the Military Capability for GCAP

On examining the GCAP military capability across seven fundamental defence domains, progress is evident, but proactive management and collaborative problem-solving remain crucial for realising GCAP's potential in shaping future air superiority.

Lofty vision: effective programme management will be pivotal to realising the ambitions for GCAP

In 2022, the Global Combat Air Programme (GCAP) between the UK, Italy and Japan was formally announced. The programme has evolved at a considerable pace since then, with the three countries signing a treaty for the establishment of a GCAP International Government Organisation (GIGO) as the international organisation to lead the collaboration in December 2023.

The treaty is the latest in the planned steps for developing the tri-country sixth-generation fighter, known in the UK as Tempest, and it cements the partnership as well as establishing its governance structures. Signing the treaty is, arguably, the easy part, and the UK and its partners must now continue to do the hard work to get the aircraft into service on time. This work includes reaching consensus on the multinational prerequisites for the initial capability, adopting a design philosophy that facilitates capability expansion over the system's lifespan, and establishing agreements on support arrangements and a continuous upgrade trajectory. It will be challenging to address all of these factors effectively, yet they are just as vital to the programme's success as overcoming the numerous technological challenges in developing a next-generation multi-role combat aircraft.

This analysis does not address the full GCAP agenda but focuses on the initial and evolving capabilities of the aircraft. It looks at aircraft-specific capability elements before addressing the capabilities of the platform as whole.

Why Sixth Gen?

There are multiple reasons for the UK’s pursuit of GCAP, including preservation and development of a notable defence industrial and technological capability and the benefits it could bring to the UK economy. More strictly in the defence domain, the governmental commitment to operational independence requires a system that can be deeply understood in order to be sustainable and modifiable in the UK. Importantly, the threat environment beyond 2040, around which the programme is directed, implies a need for a system that delivers a step change in capability from current fifth-generation aircraft (such as the F-35 and F-22). Indeed, the development of technologies driving the evolution of the threat environment is happening rapidly and is seeing massive investment from state actors. This is transforming the threat landscape significantly, thereby requiring a new capability not only to act as a deterrent but also to defeat these threats and ensure continued ability to deliver the necessary military effect. This is reflected in the US’s commitment to the Next Generation Air Dominance (NGAD) programme, aimed at replacing the F-22 fighter jets and developing a portfolio of technologies to ensure continued air superiority. Similarly, France, Germany and Spain are pursuing the Système de Combat Aérien du Futur (SCAF) programme to replace French Rafale jets and Eurofighter Typhoons from Germany and Spain.

When it comes to UK next-generation capability development, it is important to distinguish between GCAP, Future Combat Air System (FCAS) and Tempest. The UK’s next-generation combat air capability development is housed within its FCAS programme, which includes a future core platform (crewed aircraft); uncrewed aircraft of various possible various types, also known as Adjuncts or Autonomous Collaborative Platforms (ACPs); next-generation effectors (weapons), command, control and information systems; and through-life services (sustainment, upgrade and training). The GCAP collaboration is the trilateral partnership and programme that will deliver the crewed fighter (known as Tempest in the UK) component of the FCAS, which is also aligned to the Japanese and Italian requirements for a next-generation crewed combat aircraft.

It is important to understand that UK combat air platforms already operate within a wider system and have done at least since the beginning of the Second World War. The RAF prevailed in the Battle of Britain through exploitation of ground-based radars (the Chain Home system), information analysts, a ground-based command system and fighter aircraft. However, what is envisaged in FCAS is much more complex and capable than anything previously established, and its sophistication is likely to incrementally increase. Most notably, and unlike previous combat air systems, it is envisaged that the FCAS will operate in conjunction with ACPs.

Fundamental Defence Capabilities

The attributes of GCAP’s next-generation crewed combat aircraft can be analysed using the framework of the seven Fundamental Defence Capabilities (Deploy, Inform, Command, Operate, Sustain, Prepare, Protect) specified in the second edition of British Defence Doctrine in 2001. This framework offers a structure within which specific requirements can be located and assessed. As will be shown in the sections below, it is also useful for clearly relating GCAP to FCAS.


Any defence system needs to be locatable or movable to the area where it can be useful. Combat aircraft are usually flown to where they are needed from an equipped base either at home or overseas. Beyond the characteristics of an intended airfield, deployability away from a prepared base must take account of the support equipment that an aircraft needs, especially for maintenance. The US Government Accountability Office has reported that 13 C-17 flights are needed to transport the support equipment for a short-notice deployment of 12 F-35s. The less support equipment is needed, the easier deployability should be. In terms of deployment range, from a UK point of view, the RAF is likely to want more from the aircraft than the 450 miles associated with the F-35B for unrefuelled combat radius.

At the international partnership level, the three GCAP partners might also address whether they should commit to establishing and maintaining a common infrastructure for the programme, so that any partner could deploy its aircraft to another partner with the minimum testing, diagnostic and maintenance equipment.


An important question concerns what level of performance will be required of the core platform to collect a hefty amount of data and to analyse its significance onboard the aircraft. These are matters for sensors and computers with computerised integration of information, creating both an opportunity and a significant challenge.

Data could be collected from onboard radar, infrared, electromagnetic and even noise sensors that receive material from different ends of the aircraft. The Inform agenda raises the questions of cost, weight and electricity: the more sensors, the heavier and costlier the aircraft and the greater the need for electric power. To enable spiral development and its electrical needs, the power and propulsion plant should be designed with significant spare capacity.

The increased amount of data available will need to be quickly processed and integrated into a meaningful picture. It will be necessary to determine whether data synthesis will be primarily driven by human input or to what extent onboard computer facilities can be trusted to provide a clearer understanding of ongoing events and potential actions. There will be a demand and an opening for enhanced integration of AI-powered sensors onboard. However, it is crucial to be cautious about ‘conspiracies of optimism’ regarding the Inform requirements, as evidenced by the persistent delays and cost escalations seen with the F-35 programme.

With technological developments driving a rapid evolution in the threat environment, a new capability will need to be able not only to act as a deterrent but also to defeat threats as they emerge

The GCAP platform is likely to be specified to be able to be informed from the beginning by extant UK platforms including Wedgetail, Reaper, the F-35 and Typhoon. However, the RAF envisages having ACPs in service by 2030 – that is before the Tempest aircraft is ready. The extent to which the GCAP will be able to benefit from and contribute to other systems from the outset should be covered in what the Ministry of Defence’s (MoD) 2024 New Procurement Model referred to as minimum deployable capability.

There is also the issue of the compatibility of the wider system, including design philosophy and interoperability, with partners. Japan, for instance, may be influenced by any US encouragement to participate in its Collaborative Combat Aircraft (CCA) for ACP requirements, and to focus on potential US aircraft for training. The question arises whether these matters pose challenges for GCAP or if they remain distinct enough from it to operate separately.


Upon receiving analysed information, the allocation of control over GCAP capabilities between machinery and the crew, as well as the extent to which the pilot will be guided by external sources, still needs to be determined. The fact that the US, France and the UK are all pursuing a new piloted aircraft suggests that no major state is yet ready to rely entirely on autonomous or even remotely controlled systems. However, the volume of information that could be available to the pilot may means that, to avoid information overload, physical control over the aircraft may largely have to be the responsibility of a machine. The human–machine division of labour is still unclear at this stage, but developments in AI and machine learning are expected to play a significant role in supporting the pilot.

The optimum scope of a pilot’s capacity to control other airborne objects needs further work, and there will likely be learning and evolution in this area. Conceptually, the GCAP pilot may have a much wider role than that of pilots to date, directing other airborne systems as part of the FCAS or beyond, while being a key node in multi-domain operations on sea and land as well as in the air. Namely, the GCAP core platform will envisage the pilots as an integrated part of the system, with human-machine interface technologies allowing them to focus on making the right decisions at the right time and making them ‘battlespace operators’.


The operational capabilities and arrangements of the aircraft are crucial considerations. It is safe to expect it to possess the capability to engage targets across air, ground and sea domains. Additionally, determining the balance between equipping the aircraft with informational collection and distribution systems versus kinetic weapons and other effectors is essential. As emphasised in John Boyd's Observe, Orient, Decide and Act loop framework, the ability to act effectively is closely intertwined with the capacity to receive and analyse data, underscoring the importance of information and its timely analysis in decision-making and operational effectiveness.

Its range needs will be defined in terms of the breadth of missions set out in the operational requirements, the location of potential targets and the need for secure basing. Given that the sixth-generation fighter jet is for the UK and Italy the successor to Typhoon, these countries are likely to insist that it should have the capability to at least perform the equivalent air-to-air and air-to-surface roles in the future operating environment that are currently performed by Typhoon.

The aeronautical characteristics of the platform will shape its capacity to deliver needed operational capability. These include a wide range of factors such as maximum and minimum height, maximum and minimum speed, range, payload, turn capability and climb rate. To date, GCAP looks set to deliver a comparatively large platform because weapons must be stored internally to preserve low observability.


The Ukraine war has underscored the importance of a country’s ability to sustain a war effort. The Sustain element of capability is important both operationally and financially: major platforms require much more expenditure over even a decade than they did to produce. It is therefore vital to give sustainment capabilities an important place in requirement specification during the earlier stages of requirement setting and project planning. Past experience suggests that insufficient investment in these areas at the design stage can impose substantial extra cost during operational service. When Ben Wallace was defence secretary, he complained in public about the operating costs of the F-35, so the Tempest should target being less expensive to use than that aircraft, which is a significant challenge.

Sustainment encompasses a multitude of critical considerations that must be addressed. These include, among others, the deployment of necessary test and analysis equipment to operational locations, determining the requisite number and qualifications of personnel for platform maintenance, establishing reliability benchmarks for subsystems and the overall platform, ensuring ease of maintenance and repair procedures, managing inventory levels and associated costs to maintain specified aircraft availability rates, and proactively addressing obsolescence challenges. While accurately forecasting these factors before development reaches an advanced stage is inherently challenging, prioritising design for reliability and availability is a must.


The effective use of any armed force and its equipment relies heavily on comprehensive and effective training. Like the F-35, the Tempest aircraft does not include a two-seat version in its plans. Therefore, training for the GCAP countries will necessitate a combination of experience on other aircraft and simulation sessions to sufficiently prepare a solo pilot for their inaugural flight on the sixth-generation aircraft.

Integrating combat-related elements of GCAP, such as interoperability with other platforms, into simulators can potentially reduce the amount of time needed for both initial training and ongoing pilot proficiency. Live flying training is not only costly but also exposes aircraft features and performance to potential adversaries. Flying simulators, however, can potentially pose retention challenges as pilots may seek more active flying roles or opportunities in the commercial sector if confined to simulator-based training for extended periods. A delicate balance will have to be struck.

The Prepare dimension prompts consideration of the attributes required for the successor to the Hawk trainer aircraft, which also serves to train future Typhoon and F-35 pilots. Finally, within the Prepare agenda, it is essential to tackle the issue of surrogate trainers. These are more economical platforms aimed at maintaining pilot proficiency, safeguarding platform security, and enhancing pilot retention. It is worth considering how this requirement aligns with both pilot training and aggressor training needs, as there may be overlapping areas where resources and strategies can be shared for greater efficiency.


All the above elements of capability will need to be protected against hostile action which will evolve over time. Physical safeguarding of a platform encompasses its core features such as low observability, along with defensive measures like warning systems, decoys, flares and countermeasures.

For the GCAP partners, it is vital to develop a platform capable of dealing with the envisaged capabilities of anticipated adversaries post-2035

The GCAP partners must deliberate on the significance of stealth and overall low observability, considering advancements in radar technology and the trade-offs associated with carrying numerous external weapons. While it may be premature to entirely abandon aspirations for low observability, even a stealthy aircraft requires effective defensive aids.

Beyond low observability and aerodynamic performance, various options exist for aircraft self-protection. These include established defensive aids such as missile and radar warning systems, as well as weaponised countermeasures like air-to-air missiles. Additionally, the emergence of directed energy weapons, such as lasers, could become a reality by 2035.

The aircraft must strike the right balance between offensive and defensive systems, with the flexibility to adjust this balance for specific missions. Last but not least, the cyber security and cyber resilience dimensions are pivotal to protecting the core system and the overall ‘system of systems’ approach.

2035 and Beyond

Balancing requirements across the seven areas of capability for GCAP’s core platform is not simple. Yet, a crucial feature will be the ability to counter potential adversaries, with China being the primary concern due to its growing industrial prowess. Russia’s capabilities in ground-based air defence should not be under-estimated, but overall, given that defence is looking to science and civil-origin technology for major advances, it seems clear that China will overtake Russia across the board in defence by 2035, if not well before. China’s trading record suggests an increasingly assertive stance towards the West, with a readiness to sell its military products to those hostile to the West, including Russia.

For the GCAP partners, it is vital to develop a platform capable of dealing with the envisaged capabilities of anticipated adversaries post-2035, particularly those of China. Such a product would satisfy the MoD’s current concept of a ‘minimum deployable capability’.

A second core requirement to counter future evolving threats is for the system to be an ‘open system’ susceptible to spiral and even continuous development. For GCAP specifically, the MoD has embraced this iterative development with its adoption of the PYRAMID Open Mission System, an open systems approach that will make upgrades more rapid and reduce software maintenance costs.

However, the terms ‘open system’ or ‘modular system’ are always easy to say but often difficult to deliver, and they do not come without challenges. Engineers must ensure sufficient power, propulsion and internal space for upgrades beyond the minimum deployable capability. While a minimum deployable capability is clear, the route to achieving it requires careful consideration, ideally with flexibility to adapt as knowledge advances. However, while this approach is welcomed, it will be important to assess the extent to which spiral development and open system architecture allow for national customisation, and how much divergence can be permitted without endangering programme coherence.

For the ‘open system’ to develop and thrive, a healthy government–industry collaboration in each of the partner countries is crucial. This would allow for dynamic adjustments to project requirements based on evolving technology and threat assessments. The Government Accountability Office in the US has long advocated a knowledge-based approach to defence acquisition, where harder commitments are specified only as knowledge is advanced. This was not the case with the F-35 which subsequently suffered multiple delays and cost overruns. Furthermore, the issue extends to government–private sector relations, where the UK and US aim to possess the intellectual property for system modifications.


As of spring 2024, significant progress can be observed, as evidenced by two key developments. Firstly, the signing of the treaty establishing the GCAP International Government Organisation signifies a notable milestone, cementing the commitment among the three partner countries and laying down governing structures for the programme’s progression. Secondly, and relevant to the capability aspects addressed in this article, consensus has been reached by the three countries on an initial system requirement document. This not only indicates a robust collaborative approach, but also shows considerable advancement in delineating the characteristics of the platform.

Amid these achievements, several complexities and challenges remain. The establishment of an industry delivery structure stands as a crucial yet pending task. It would be reassuring if this structure is announced by the end of the year, and delays beyond this point could pose concerns. Additionally, there are important issues that will have to be addressed such as in-service support arrangements, security and vetting considerations for personnel (especially in light of recent Chinese espionage cases), exports arrangements and potential collaboration with third countries on sub-systems.

The success of GCAP hinges not only on the development of the aircraft itself, but also on avoiding ‘conspiracies of optimism’ and addressing problems collaboratively as they emerge. The challenges and opportunities outlined in this article can inform the GCAP partners in their next steps towards 2035. Effective programme management, including timely decision-making, will be pivotal to realising the vision of the GCAP team.

The views expressed in this Commentary are the authors’, and do not represent those of RUSI or any other institution.

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