Fuelling the future fight: Inside the USAF’s 100th Air Refuelling Wing

Air-to-air refuelling (AAR) is vital to projecting and sustaining combat air power, especially in high-intensity conflicts. The US Air Force’s 100th Air Refuelling Wing, therefore, is at the forefront of tactical changes in Europe that aim to ensure fuel – and therefore combat air power – remain available wherever, and whenever they are required. Air-to-air refuelling (AAR) is the lifeblood of modern air power projection, underpinning its core tenets: reach, persistence and ubiquity. Yet, in today’s contested air environment, shaped by advanced Anti-Access/Area-Denial (A2/AD) strategies, the high-value, yet extremely vulnerable tanker aircraft that fulfil this role face mounting risks.

In high-intensity conflict, reliable and punctual fuel delivery has become both more difficult and more critical. Current tankers, however, due to their size, limited manoeuvrability, and predictable flight paths are particularly exposed, risking becoming large, slow-moving targets.

 

Nevertheless, AAR remains critical to enabling persistent surveillance, accelerating logistics, sustaining combat air patrols, and supporting high-tempo Suppression of Enemy Air Defence (SEAD) missions. Tankers set the pace, endurance and survivability of air operations, ensuring sustained pressure against adversary forces and resilience against advanced threats.

This evolving threat landscape is driving a shift in mindset and tactics within the United States Air Force (USAF). Leading that change in Europe is the 100th Air Refuelling Wing (ARW), based at RAF Mildenhall in the United Kingdom. As the USAF’s only permanent refuelling unit in Europe with 17 KC-135R/T Stratotankers assigned, the Wing anchors the region’s AAR and airlift ecosystem, supporting US, NATO and allied forces, while constituting the continent’s largest single tanker fleet.

The 100th ARW is spearheading efforts to prepare for operations in contested environments, by advancing new tanker tactics to enhance survivability, efficiency and mission effectiveness. Captain Andrés Vélez, Chief of Tactics for the 351st Air Refuelling Squadron – the Wing’s flying component – described this emerging doctrine as being “in its genesis.” According to Capt Vélez, these evolving concepts are reshaping how tanker assets are tasked, integrated, and employed in combat, ensuring, as he put it, “the continuity of [fuel] offload” in increasingly complex and contested environments.

The 100th ARW and the European AAR picture

As the 100th ARW adapts to emerging challenges, its role must be viewed within the context of Europe’s evolving AAR landscape. Throughout the past decade, Europe’s AAR capabilities have faced persistent scrutiny. In 2013, the European Defence Agency identified AAR as one of four critical capability shortfalls. In response, the Multirole Tanker Transport Unit (MMU) was established in 2019 under a joint NATO-EU framework. The MMU provides participating states access to a pooled fleet of A330 Multi-Role Tanker-Transport (MRTT) aircraft by purchasing flight hours (See Table 1), offering strategic airlift and AAR capacity without the cost burden of sovereign ownership.

Table 1: Current NATO MMU membership
Operator	Purchased flight hours per year
Belgium	1,000
Czech Republic	100
Denmark	None yet
Germany	5,500
Luxembourg	200
Netherlands	2,000
Norway	100
Sweden	None yet
Note: Flight hours not yet announced for Denmark and Sweden, since they only recently joined on 24 June 2025. Finland is also slated to become a member, having signed a letter of intent to join on 5 June 2025.

 

Meanwhile, Table 2 outlines Europe-based dedicated tanker fleets, excluding aircraft equipped with roll-on/roll-off solutions, such as Germany’s A400M Atlas or the (K)C-390, due to limited public data on their configuration status. Tankers primarily used for rotary-wing support, such as the KC-130J, are similarly excluded, due to niche operational uses.

Table 2: Dedicated European tanker fleets
Country	Aircraft Type	Fleet Size	Refuelling Type
France	A330 MRTT ‘Phénix’	12×	Boom Hose & drogue
France	KC-135RG	3× (to be retired by end of July 2025)	Boom Hose & drogue
Italy	KC-767A	4×	Boom Hose & drogue
NATO MMU	A330 MRTT (KC-30M)	9× (+3 on order)	Boom Hose & drogue
Spain	A330 MRTT	3×	Hose & drogue
Türkiye	KC-135R	7×	Boom Boom-drogue adapter
United Kingdom	A330 MRTT ‘Voyager’	4× KC Mk.2 (wingtip pods only) 7× KC Mk.3 (wingtip pods + centreline hose)	Hose & drogue
USA	KC-135RT Stratotanker	17×	Boom Boom-drogue adapter 4x aircraft compatible with MPRS

 

As Table 2 highlights, AAR is delivered through two primary systems:

• Flying boom: a rigid, telescopic tube that is manually controlled by a boom operator and manoeuvred into a receptacle on the top of a receiver aircraft. The boom is primarily used by the USAF due to its generally higher fuel offload rates.
• Hose-and-drogue: a flexible hose fitted with a shuttlecock-like basket that connects to a ‘probe’ on a receiver aircraft. Hose-and-drogue has historically been widely used among non-US NATO member states, as well as the US Navy and Marine Corps, due to its simplicity and adaptability.

Growing European AAR capabilities have meant that a physical dependence on US tankers has somewhat decreased throughout recent years. However, many European air arms continue to lack any tanker provision at all – meaning the 100th ARW remains indispensable, particularly as European fighter fleets grow and calls for further proliferation mount to counter ever-growing threats on NATO’s Eastern Flank.

In this vein, Europe now faces a growing imbalance between tanker assets and the expanding number of boom-only receiver aircraft. While hose-and-drogue remains prevalent in NATO inventories, the growing presence of F-35A Lightning II fighters – which require boom refuelling – is shifting the balance. While the ‘B’ and ‘C’ variants of F-35 use hose-and-drogue, Lockheed Martin projects that by 2030, Europe will host over 550 F-35s, of which the majority will be the ‘A’ variant. Additionally, new F-16 acquisitions by Bulgaria and Slovakia will further strain boom capacity.

The 100th ARW’s KC-135s are uniquely suited to meet this demand. Each aircraft is equipped with a 5.6-metre ‘flying boom,’ capable of transferring fuel up to 2,722 kg/min depending on the receiver aircraft. In addition, all the 100th ARW’s KC-135s can be reconfigured with a Boom-Drogue Adapter (BDA) – a 2.74-metre hose affixed to the boom to refuel probe-equipped aircraft at approximately 1,270 kg/min. However, this configuration prevents conventional boom use.

Further versatility is provided by the Multi Point Refuelling System (MPRS); 20 USAF KC-135s can be outfitted with Cobham wingtip pods, enabling simultaneous refuelling of two probe-equipped receivers at approximately 1,215 kg/min, while maintaining boom capability on the centreline. Four of these aircraft are based at RAF Mildenhall.

These capabilities place the KC-135’s performance on par with other contemporary tankers, such as the A330 MRTT and Italy’s KC-767A. Both aircraft can offload fuel up to approximately 1,300 kg/min via hose-and-drogue systems, while their boom systems can reach up to 3,600 kg/min and 2,725 kg/min, respectively.

 

The high demand for boom-capable tankers makes the 100th ARW a critical component of Europe’s AAR infrastructure, helping European NATO member states meet rising AAR demand – particularly by ensuring the continuity NATO-standard training under Allied Tactical Publication 3.3.4.2, the governing doctrine for AAR between Alliance members.

Building a credible tanker force: Exercise Ramstein Flag 2025

Although Europe’s AAR capabilities have improved, they will remain under pressure so long as NATO’s fleets of receiver aircraft continue to expand. The issue is, therefore, no longer simply whether NATO has enough tankers, but how to maximise the flexibility and efficiency of the assets already in service. Given the Alliance’s diverse AAR fleet, platform integration allows it to leverage each platform’s strengths and distributing demand to reduce the burden on specific platforms or operators.

Exercise Ramstein Flag 2025 (RAFL-25), conducted from 31 March to 11 April, placed particular emphasis on how NATO’s tanker platforms could work together more effectively in a demanding operational setting. For the AAR component, this focussed on improving resource management and enhancing cross-platform integration – not only between receiver and tanker aircraft, but among tanker types themselves. For example, the KC-135 carries approximately 90,719 kg of fuel, whereas the A330 MRTT offers a larger load of around 111,000 kg, making it well-suited for longer-endurance missions. Italy’s KC-767A, with a receptacle capability, extends its own range by receiving AAR itself.

The UK’s Voyager fleet, meanwhile, currently operates exclusively in a hose-and-drogue configuration. Its seven Voyager KC.3s incorporate a centreline drogue unit that can offload fuel at up to 1,800 kg/min, making it suited for for widebody, probe-equipped receivers, such as the A400M Atlas, where greater fuel flow and tanker-receiver separation is required. These capability variations mean that each tanker variant may be better suited for a different task. As such, the allocation of resources can be determined based on these factors to minimise waste and maximise efficiency.

Based on these principles, RAFL-25 served as a proving ground for the concept of dynamic air refuelling – an evolution of traditional AAR frameworks that moves beyond fixed schedules, rendezvous points and offload plans. Dynamic AAR introduces real-time flexibility, matching offload requirements and tanker availability task-by-task. As Capt Vélez explained, dynamic AAR means “not necessarily knowing what your offload is going to be until the day [of the mission],” enabling adjustments for aircraft serviceability, shifting operational demands and battlespace conditions.

To support this, each participating tanker unit (See Table 3) embedded liaison personnel at a central coordination facility at Leeuwarden Air Base, The Netherlands. There, mission planners assessed daily receiver needs, balancing factors such as fuel consumption rates, tanker offload capacity, combat radius, and threat assessments. Based on this, tankers were tasked based on where it made strategic sense to employ each specific tanker type for a given mission.

Table 3: Exercise Ramstein Flag 2025 – participating tankers
NATO MMU	A330 MRTT (KC-30M)	Boom Hose & drogue
United States Air Force	KC-135R Stratotanker	Boom
Turkish Air Force	KC-135R Stratotanker	Boom
Royal Canadian Air Force	A310 MRTT	Hose & drogue
Royal Air Force	Voyager	Hose & Drogue

 

Crews then optimised their own planning based on this guidance, adjusting for local variables such as weather or emergent threats. This layered approach – centralised coordination with decentralised execution – enabled real-time responsiveness while maintaining cohesion across the tanker force.

The mission observed by the author on 9 April 2025, illustrated the practical benefits of this new, dynamic approach. For the first time, a USAF KC-135 and an RAF Voyager flew a mixed formation, refuelling two different receiver aircraft types simultaneously. According to Capt Vélez, this allowed “two very capable [combat air] platforms to peel off together and support a defensive line.”

Yet what does this mean in context? While the MMU’s A330 MRTTs are equipped with both boom and hose-and-drogue systems, the aircraft cannot operate both simultaneously, necessitating sequential refuelling, preventing platforms such as the Eurofighter Typhoon and F-35A from refuelling concurrently, reducing efficiency and operational tempo. As such, by leveraging two tanker aircraft of differing configurations, the refuelling process was accelerated, extending the persistence and effectiveness of fighter aircraft. Less resource was also wasted where a queue for the tanker would otherwise form, increasing fuel burn and reducing overall combat effectiveness.

 

In context, this would help ensure that critical systems are not simultaneously withdrawn for refuelling, preserving massed effects in contested airspace. For instance, in a SEAD context, low-density, high-value aircraft assigned to the role, such as F-35s or the E/A-18G Growler, each requiring different refuelling systems, can remain persistent and can exploit narrow opportunity windows – such as radar deactivations – to conduct time-sensitive strikes while others cycle through refuelling. The RAFL-25 sortie thus demonstrated how smart integration, not just fleet expansion, will prove key to sustaining NATO’s airpower edge.

Advantages of a networked tanker

While physical interoperability among NATO tanker platforms enhances operational flexibility, realising their full potential requires a shift toward networked operations. In the increasingly complex and contested air domain, tanker aircraft must evolve from simple fuel providers into connected battlespace nodes – capable of supporting, adapting and surviving within rapidly-changing environments.

This aligns with the principles of Joint All Domain Command and Control (JADC2), which seek to create a unified ‘Common Operating Picture’ (COP) across operational domains. For tanker crews, access to this near real-time battlespace overview – including asset positions, threat updates and mission priorities – enables decentralised decision-making. This is crucial for sustaining fast-paced operations, where windows of opportunity may only last minutes.

As Capt Vélez observed, effective communication is the cornerstone of modern AAR operations. With access to the COP, tanker crews can anticipate receiver needs, reposition to reduce transit time and ensure optimal fuel offload availability – often without needing higher-level tasking. On the KC-135, this connectivity is currently facilitated by two core systems:

• Roll-On Beyond Line-of-Sight Enhancement (ROBE) and
• Real Time Information in the Cockpit (RTIC)

ROBE, introduced in the early 2000s, allows KC-135 crews to process, and relay data that has been converted into an accessible format between dispersed assets, beyond the line-of-sight. More recently, RTIC has added near-real time Link-16 integration, providing live tactical feeds directly to the crew. According to Capt Vélez, RTIC displays voice, text and visual depictions of the battlespace across three cockpit displays.

According to Rockwell Collins’ (now Collins Aerospace) open-source product data from 2012, RTIC leverages the company’s Flight Information Management System (FIMS), an open architecture solution designed to integrate into existing avionics. The system supports installed and portable displays, ranging from multifunction displays (MFDs) to tablets, so that crews can view tactical overlays, such as aircraft data over moving maps that also highlight threats, friendly forces, obstacles, and real-time weather.

RTIC supports secure data sharing through communication links such as Link-16 enabling tools like email, text-based messaging, and file transfer – including video and still images. By integrating information from systems such as GPS, Radar Warning Receivers, and intelligence feeds, it enhances decision-making, enables dynamic mission planning, and improves situational awareness across the battlespace.

 

This transforms the tanker’s responsiveness, allowing crews to monitor assets positions, ongoing actions, and fuel statuses, and potential threats – without relying on intermediaries, such as AWACS. Instead of relying on relayed messages, Capt Vélez described the process as akin to a receiver simply transmitting: “Hey, I need gas,” allowing tanker crews to quickly assess fuel availability and reposition accordingly. The result is decreased reliance on congested voice channels, faster re-tasking and improved fuel utilisation, without relying on intermittent transmissions from third parties.

Situational awareness also extends beyond fuel logistics, as access to real-time weather and threat data allows tankers to re-route dynamically for survivability or mission continuity. Consider a simple Close Air Support (CAS) scenario: A Joint Terminal Attack Controller (JTAC) requests immediate engagement against advancing adversary ground forces. A flight of F-35s, low on fuel from a previous engagement, must refuel before re-engaging. Here, the tanker becomes a critical decision-making node. With near real-time data on the fighters’ locations, fuel states and airspace threats, the tanker adjusts its orbit proactively, reducing the combat-radius and making the fighters available to support the JTACs, sustaining pressure on the adversary.

Networked tankers also benefit from shared threat intelligence. Their size and profiles make them vulnerable targets. Situational awareness, particularly in contested environments is thus imperative to survivability. When assets such as fighter aircraft are networked with tankers, they can significantly extend the latter’s situational awareness, helping them to notice and avoid threats in contested environments.

Closer, lower, smarter: tanking under threat

As datalink connectivity enhances the KC-135’s integration within the broader battlespace, its evolving role as a force enabler also makes it a higher-value target. For tanker operations, this can constrain viable operating areas, pushing refuelling tracks further from the front lines, extending receiver transit times for receivers, increasing overall fuel consumption, and ultimately degrading their endurance and responsiveness. Capt Vélez captured this with a simple analogy: “If Johnny has a heavier baseball and can hit me from further away, then that means I [the tanker] cannot get closer – and therefore the fighters cannot get closer.” This underscores a critical dependency: the effectiveness of combat air power is contingent on the availability and survivability of tanker aircraft.

As such, the KC-135’s comparatively smaller radar cross-section (RCS) and relatively high agility (compared to many other tankers) make it well-suited for the development of experimental tactics focused on survivability. Among these is low-altitude employment, an unconventional approach for large, non-tactical platforms. In this vein, the 100th ARW has been trialling flight profiles that leverage terrain masking to reduce radar exposure, allowing the aircraft to operate closer to contested areas without confinement to standoff ranges.

This principal rests on basic physics: under most circumstances, fire control radars used by air defence systems are limited by line-of-sight (LoS), meaning their signals travel in straight paths and cannot bend around terrain. As such, hills and mountains can block or disrupt the signal, thereby ‘masking’ an aircraft using such terrain as cover. Through careful route planning to maximise terrain masking opportunities, tankers can reduce their exposure and operate closer to receiver aircraft. This approach does have limits, notably against airborne radars, which face fewer LoS obstructions at typical flight altitudes.

Historical precedent for this tactic exists. During the Cold War, the USAF’s Strategic Air Command explored similar employment methods. A 1988 report by Major James L. Day, published by the USAF’s Air Command and Staff College confirmed the KC-135’s strong low-altitude handling and emphasised that ingress routes could be planned using known radar positions, allowing the aircraft to follow fighters closer to target areas.

 

Today, the 100th ARW is pushing these boundaries by “going outside of the comfort zone of what we think is normal and testing those limits to see if it makes us more effective in that future evolution [of warfare],” according to Capt Vélez. ESD enquired whether future iterations of this tactic might include the ability to offload fuel to fighter aircraft at low altitudes. Vélez confirmed that this option has been explored but is not currently part of training programmes.

Among boom-capable tankers, the KC-135 remains the most viable candidate for low-level ingress. Its smaller size and higher manoeuvrability allow it to take risks in narrow terrain corridors which may be unacceptable for larger, less agile platforms such as the A330 MRTT or KC-46. While some hose-and-drogue platforms, such as an A400M fitted with a RORO hose-and-drogue kit, can support tactical ingress, the lack of a suitable boom equivalent limits the range of aircraft they can support. For now, the KC-135 stands out as the most promising candidate for low-level AAR operations in contested environments.

ESD also discussed the risks associated with the standard ‘towline’ pattern commonly used in day-to-day AAR operations in the context of contested environments. Traditionally, a towline involves a fixed racetrack-style orbit flown at a pre-determined altitude within a designated AAR track. While effective in permissive environments, this predictability leaves tankers vulnerable to adversaries equipped with long-range sensors and weapons. Capt Vélez confirmed that this is recognised and is actively driving further innovations.

One such solution is the use of ‘unique geometry’ – non-standard refuelling patterns designed to reduce predictability and complicate adversary targeting. Without disclosing operational specifics, Vélez explained that these tactics are developed through close collaboration between intelligence specialists and platform-specific tacticians who integrate threat information and aircraft performance characteristics to devise effective, dynamic AAR solutions. As threats evolve, the KC-135’s adaptability, through connectivity, low-level ingress and development of flexible refuelling tactics are ensuring it remains a relevant enabler in contested environments.

Keeping KC-135 in the skies

The 100th ARW sustains a high operational tempo as a ‘deployed-in-place’ unit, simultaneously supporting real-world missions and routine training – a model that can strain aircraft availability. Nearing 70 years in service, NATO’s oldest AAR platform could remain viable into the 2050s under a proposed recapitalisation plan. In the meantime, sustaining the aircraft’s day-to-day viability depends on rigorous preventative maintenance and upgrade procedures.

100th Aircraft Maintenance Squadron (AMXS) personnel told ESD that, of 17 aircraft, 14-15 are usually on station, with 8-9 mission capable. This performance is underpinned by proactive maintenance practices driven by detailed data analysis to identify recurring faults and implement root-cause solutions – minimising downtime and ensuring aircraft availability.

 

The 100th AMXS conducts maintenance up to the intermediate level to include isochronal inspections, wherein each aircraft is partially disassembled to inspect and replace key components. Such inspections are vital given Europe’s diverse climates, from the cold temperatures of the Arctic to the corrosive salty air of the Mediterranean. For many maintainers, this is their first posting, meaning they work extremely hard, while gaining vital experience in these high-tempo conditions.

To maximise sortie generation, the 100th ARW is trialling two accelerated turnaround methods: ‘Hot gassing’ and ‘Rapid refuel.’ During ‘hot gas’ operations, the aircraft lands and refuels as its engines continue running, usually completing within 2-3 hours. By contrast, ‘Rapid refuel’ shuts down the aircraft, leaving only the Auxiliary Power Units running.

ESD was told that each method has advantages and disadvantages. During a ‘hot gas,’ the aircraft is handed over to maintenance teams, allowing them to inspect the aircraft in detail. However, as the aircraft is refuelled, it is immediately burning fuel. Meanwhile, a ‘rapid refuel’ burns less fuel and can be completed more quickly, however, it requires tight coordination between different agencies on the base, complicating the process.

While unorthodox for a platform like the KC-135, and currently only trialled in peacetime, these practices could prove vital in a high-intensity conflict. In scenarios where airfield survivability poses a risk to operations, and tanker resources are limited, sortie generation must occur rapidly. Therefore, safely compressing turnaround times will prove essential to sustaining AAR and meeting elevated demand from receiver aircraft. Even after seven decades in service, the KC-135’s blend of operational flexibility, maintainability, and innovation readiness ensures it remains a critical pillar of NATO’s air power projection.

Lessons learned

Spending time with the 100th ARW makes one thing clear: tankers are now decisive nodes, not just passive enablers. In any operational context, the number of tanker resources will always be fewer than fighter aircraft, creating two core imperatives: maximising resource utility and ensuring their survivability.

Europe already possesses a diverse array of AAR capabilities, which, when effectively mobilised, offer significant potential. Unlocking this potential requires leveraging each platform’s unique strengths through tailored, innovative solutions.

The emergence of RORO kits, for instance, enables tactical hose-and-drogue refuelling options that supplement larger, less agile tankers. For instance, the A400M’s tactical airlift capabilities, coupled with its RORO AAR potential, remains untapped by the UK, but offers scope to bolster capacity to refuel aircraft such as Gripen and Typhoon in environments unsuitable for less-agile tankers.

The 100th ARW underscores that survivability, connectivity and adaptability will shape the tanker force of the future. By embracing adaptability, survivability and seamless connectivity, the future tanker component will not only support operations but also shape them.

Luca Chadwick