The United States and Europe share the same fighter jets, but technical and logistical differences often prevent them from repairing each other’s aircraft within NATO.
In summary
On paper, sharing F-35s or F-16s between allies should simplify things: same parts, same procedures, same technicians. The reality is less straightforward. A September report highlights that variants of the same model, incompatible ground equipment, and the lack of shared technical data often prevent one ally from repairing another’s jet. The result: delays, additional costs, reduced availability, and continued dependence on national supply chains. Interoperability is not only hampered by technical issues; it also faces obstacles in the form of ITAR security, data rights, cryptography, and heterogeneous maintenance standards. However, there are ways forward: harmonizing procedures, certifying cross-maintenance, sharing critical tools, creating regional hubs, and opening up greater access to data (ODIN/ALIS). The challenge is clear: without rapid progress, the ambition to operate “as a single force” will remain theoretical.
The observation: expected synergies that are not materializing
Ideally, operating identical F-35s and F-16s makes it possible to exchange parts, borrow missing tools, and entrust inspections to a partner’s team. At the European level, nearly 600 F-16s are in service outside the United States, spread across half a dozen blocks: F100 or F110 engines, OBOGS onboard oxygen systems of different generations, analog or digital controls. This mosaic prevents true standardization and limits the “plug-and-play” exchange of parts and skills. The report points out that even when the aircraft is called an F-16, the block, engine, and avionics suite can tip the balance of compatibility from “yes” to “no” operationally. For the F-35, differences in software standards and data governance complicate day-to-day mutual assistance just as much.
The heart of the problem: variants, tools, and data
Three types of obstacles stand out.
Variants that fragment support
Each block of a fighter jet has its own specific features: accessory attachment points, interfaces, torque settings, diagnostic software. A pump or valve that is “almost” identical becomes interchangeable if the reference number differs. At the fleet level, this granularity increases inventory, lengthens lead times, and prevents simple cross-maintenance tasks from being performed.
Incompatible ground equipment
The same type of aircraft may require different test benches, cables, pins, harnesses, hydraulic carts, or nitrogen. As a result, an ally hosting partner jets cannot connect its test bench to the visiting aircraft due to a lack of certified adapters. The RAND study lists SE (Support Equipment) as the “Achilles heel”: without a minimum common standard, teams cannot diagnose or release the aircraft safely.
Data and procedures that are not shared
Technical Orders, maintenance histories, service bulletins, interface diagrams, and parts lists are often protected by ownership clauses, access licenses, or distribution restrictions. Without the documentation, a qualified technician does not have the right—and sometimes the means—to intervene. On the F-35, dependence on the “digital thread” (ALIS then ODIN) and access rights reinforces this barrier.
Political and legal constraints: security, cryptography, and ITAR
Beyond ratchet wrenches, modern maintenance touches on sovereignty: Mode 5 encrypted IFF modules, electronic warfare libraries, signature parameters. Authorizing a partner to connect an analyzer to these subsystems requires a legal agreement (ACSA, implementing arrangements), crypto clearance, and non-disclosure validation. ITAR security limits what can be shared, despite the goal of interoperability. The authors recommend anticipating these obstacles in operational plans, rather than negotiating under the pressure of a breakdown or crisis.
The F-16/F-35 example: same aircraft, different realities
The F-16 illustrates European complexity: multiple blocks, local modernizations, national avionics, and case-by-case integrated munitions. In practical terms, an F-16 Block 50 with an F110 engine is not “maintainable” like a Block 30 F100. The exchange of critical parts may be impossible without requalification. For the F-35, the platform is more homogeneous, but access to health data (HUMS) and batch software management (Tech Refresh, mission updates) require synchronization that not all partners achieve at the same pace. A successful experiment in cross-maintenance of the F-35 between Nordic allies has shown that it is feasible… provided that common tools, certifications, and procedures have been prepared.
The operational costs of false interoperability
The promise of a “common fleet” erodes as soon as a foreign jet lands at a friendly base. If the host cannot take advantage of its stocks and teams, the aircraft remains grounded until a national kit arrives. Each day of downtime degrades availability and weighs on the mission. On the scale of an air campaign, the cost is high: lost flight hours, ferry flights, duplicate stocks, emergency contracts. Agility/ACE supply chain architectures, designed for dispersion, rely precisely on local mutual assistance; without shared maintenance, ACE becomes a headache.
Invisible dependencies: software, calibrations, standards
An increasing proportion of tasks are performed using software and instrumented benches. However, calibrating an actuator, purging a fuel loop, or validating an inertial sensor requires software, test profiles, and sometimes a connected license. If the ally does not have the right version, the task is legally or technically impossible. The same problem applies to calibrations: different metrological standards can invalidate a flight release. Here again, the solution lies in “interoperability packages” planned in advance (versions, keys, licenses, adapters, procedures).
Pragmatic solutions proposed by the research
The report sets out a series of actions, prioritized for the short, medium, and long term.
Common procedures and cross-certification
Create shared intervention checklists, validate transferable “standard tasks,” and issue common certificates for defined maintenance levels. Objective: to enable a partner to legally and technically perform a 50-hour inspection, accessory replacement, or functional test without systematically referring back to the country of origin.
Interoperable ground equipment kits
Establish a shortlist of critical equipment (benches, cables, special tools) and provide duplicates at host bases, or create mobile kits for ACE deployments. These kits must include certified adapters for multiple blocks and multilingual instructions.
More open data governance
Give partners conditional access to the necessary technical data (TO, bulletins, history) via secure portals, with clear traceability and scope. On F-35, adjust ODIN access profiles so that allies can view and act on basic tasks without touching sensitive “black boxes.”
Regional hubs and framework agreements
Pool component repairs (standard exchange), organize parts pools, sign cross-support agreements, and create certified regional centers. The goal is to reduce logistics travel and downtime.
A ready-to-use legal framework
Pre-negotiate implementation arrangements (ACSA, technical annexes), crypto clauses, and ITAR security to enable immediate mutual assistance as soon as an allied jet lands.
What this means for a squadron in operations
In practical terms, a foreign F-16 that has been diverted should be able to connect to the local test bench, read its faults, replace a hydraulic line, test the OBOGS, and take off again within 24 hours. To achieve this, the host squadron must have the adapters, its mechanics must be certified, the documentation must be legible, and the software tool must accept a partner’s signature. In a contested theater, cross-maintenance is no longer a luxury; it is a tactical condition for survival for air forces scattered across several short-runway airfields (800 to 1,200 m), vulnerable to missiles and drones.
The risks if nothing changes
Without change, allied forces will continue to accumulate micro-frictions: grounded jets, duplicate purchases, dormant stocks, incompatible tools. The ambitions of ACE deployments will lose credibility, and adversaries will know that the “common fleet” is nothing more than a label. Interoperability is measured on the day a foreign aircraft makes an emergency landing and takes off again the next day. As long as this use case remains the exception, NATO is not exploiting the colossal industrial advantage of sharing platforms.
A realistic goal: standardize without sacrificing sovereignty
Making things compatible does not mean sharing everything. There is a middle ground: standardize “non-sensitive” tasks, pre-certify maintenance levels, share limited data sets, secure access, and keep electronic warfare, cryptography, and stealth signature under national control. In short, open up what is necessary and protect what is strategic. Technology is not the main obstacle; it is governance, contractualization, and anticipation that will make the difference.
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