COCO air refuelling: Planting the seed of resilience

Air-to-air refuelling (AAR) is vital for projecting air power persistently and at range. However, building sovereign tanker capabilities can be costly and slow. Contractor-owned, contractor-operated (COCO) AAR offers scalable, on-demand capacity and should be considered by European and NATO planners.

In a COCO model, a private company provides an aircraft, its crews and support, akin to a ‘wet lease’ in commercial aviation. This operational model has become increasingly common within the defence sector, typically performing niche functions and possessing capabilities comparable to those of front-line military units – operating former military aircraft and employing large numbers of former service personnel with experience in their respective fields. This allows these companies to function almost indistinguishably from traditional military squadrons.

The spectrum of COCO services spans Intelligence, Surveillance, and Reconnaissance (ISR), adversary air training, and AAR. Each of these domains relies on high-end, expensive-to-procure capabilities that are typically in short supply and ever-increasing demand. AAR is, hence, one area in which this is felt most acutely, with several drivers of demand, including:

• Pilot training pipelines to create new pilots and up-skill front-line aircrew as receivers.
• Enhancing deterrence and ISR persistence in volatile security environments through AAR, enabling sustained air policing patrols and continuous surveillance.
• Expanding global operational theatres demands rapid responsiveness and flexibility, which in turn require robust AAR capabilities.

COCO services can thus provide air arms with a plug-and-play capability that can supplement, or in some cases substitute for, limited sovereign resources.

Assessing challenges in high-demand AAR fleets

The United States Air Force’s ‘Mobility Capabilities and Requirements Study’ (2019) estimated a need for 479 tankers by 2023 to sustain “wartime missions,” based on a “fully mobilised joint force.” This hence excluded routine receiver training, a cornerstone of AAR operations and an unavoidable driver of demand.

As James ‘Slim’ Morgan, President of Metrea Strategic Mobility, explained to ESD, strained tanker fleets limit training opportunities, making it difficult to qualify new crews and sustain proficiency among existing ones. Therefore, without dedicated training capacity, qualification timelines slip, proficiency erodes, and shortages of trained crews may emerge, directly threatening combat readiness. Morgan summarised this simply: “If you don’t train, then you’re not going to be able to field forces down the road.” Recognising this, the COCO AAR industry is positioning itself to provide additional capacity to meet increasing needs where units requiring training are underserved.

 

This challenge is not unique to the US. Europe faces similar pressures as it works to close its long-recognised shortfall in tanker capacity, first identified by the European Defence Agency (EDA) in 2013. The European Air Transport Command (EATC) has led this charge, notably through the NATO Multinational Multi-Role Tanker-Transport (MRTT) Unit (MMU), which will soon comprise 12 A330 MRTTs. In parallel, France has replaced its fleet of KC-135s with a further 14 A330 MRTTs, while France, Spain, and Germany now operate AAR-capable A400M fleets using Roll-On/Roll-Off (RORO) hose and drogue kits, while a Franco-German KC-130J tanker squadron adds further hose and drogue AAR capacity.

Yet, even as Europe expands its fleets, real availability can be constrained by high demand and the practical realities of maintenance and attrition. The MMU is already contracted to deliver close to 9,000 flying hours annually across all its participants, a figure which set to rise as additional states join the initiative. Meanwhile, Europe’s RORO platforms are limited to hose-and-drogue refuelling, meaning they cannot support Europe’s growing inventory of boom receivers.

Nevertheless, the EATC’s commander, General Franck Mollard, underlined in 2024 that the organisation must prepare for “conflicts whose intensity would far exceed that of the conflicts of recent decades.” For AAR, this equates to one simple task: reconciling the competing demands of operations, training, and surge readiness within inherently limited fleets.

Even the best-equipped forces rarely enjoy the full strength of their fleets, as aircraft are frequently unavailable due to inspections, scheduled maintenance or unexpected technical issues. Thus, increased operational use will shorten maintenance intervals, further tightening availability. High-intensity conflict also increases the risk of attrition losses, as tankers are inherently vulnerable assets, and replacements cannot be procured quickly. As such, any losses would leave significant and lasting gaps.

Here lies the strategic value of COCO AAR. By adhering to NATO’s Allied Tactical Publication (ATP)-3.3.4.2, commercial providers align with established equipment standards, procedures, and safety protocols. This ensures interoperability across both types of refuelling systems, allowing crews to translate training directly into operations regardless of the tanker aircraft type. COCO services can therefore function as a true supplement to NATO fleets, protecting training pipelines in peacetime and bolstering operational output when demand surges.

Ultimately, sustaining readiness demands more than just enough tanker aircraft and combat mass. Achieving true readiness demands the safeguarding of training capacity against the pressures of limited fleets and growing operational commitments. COCO AAR thus helps ensure this capacity.

Sustaining operations

Morgan noted a further key advantage of COCO tankers in that, once contracted, they remain dedicated to their assigned missions, providing a level of reliability that military assets cannot always guarantee. Military-controlled tankers can often be diverted to higher-priority operations at short notice, often leaving training sorties or scheduled deployments under strain.

This has a direct impact on scheduled long-distance aircraft movements, where a break in tanker support can delay force packages and create bottlenecks, as assets remain static without dedicated tankers. This risk can, however, be directly tackled by leveraging COCO AAR resources.

In 2023, for example, as a group of USAF F-35As redeployed from Hawaii to their home base in the United States, MSM was able to rapidly provide two KC-135s to support their return. Once assigned, these aircraft remained with the fighters until the mission was complete, ensuring uninterrupted support. This same principle has also proved effective in Europe. During Exercise ‘Pacific Skies’ in 2024, MSM KC-135s augmented two MMU A330 MRTTs to support German Air Force Eurofighter Typhoons as they moved throughout the Indo-Pacific, serving as the primary tankers for one element of the deployment, demonstrating COCO AAR’s ability to integrate with military forces, under their operational control.

Morgan explained that, while for now this value helps ensure aircraft can get from A to B punctually during exercises or routine operations, this benefit could extend into real-world operations. He suggested that COCO tankers could sustain the flow of personnel, equipment, and aircraft into a theatre of operations “from behind,” allowing military assets to focus their efforts closer to the battlespace.

 

Hypothetically, this could involve the strategic placement of COCO tankers at pre-determined launch and recovery points along Eastern Indo-Pacific transit routes. This would help them to sustain the flow of airlift aircraft, such as C-17s, as they travel vast distances to reinforce the region without the need for frequent landings. In Europe, an equivalent application might see COCO tankers supporting the movement of fighter aircraft from the US mainland across the Atlantic Ocean as they manoeuvre to reinforce Europe, allowing military tankers to focus on sustaining persistent combat air power along the front lines.

Importantly, however, COCO AAR should not be seen in this sense as a substitute for national capability development or improving resource management, such as the US-UK tanker integration observed during Exercise Ramstein Flag 2025 (See: ‘Fuelling the future fight: Inside the USAF’s 100th Air Refuelling Wing’ in ESD 07/08-25). Instead, its strength clearly lies in providing a cost-effective buffer that reduces strain, mitigates bottlenecks and ensures consistent AAR capacity to meet rising demand across both training and operations.

Industry leaders

Two US-based firms currently lead the COCO AAR market: Metrea Strategic Mobility (MSM) and Omega Air Refuelling Services (OARS). Both have supplied the US Department of Defence and are expanding internationally, with MSM’s recent contracts in Germany and India.

Omega Air Refuelling Services

OARS represents the longest-serving private AAR company, founded in 1999, and has subsequently spent two decades supporting the United States Navy and Marine Corps’ routine fleet training.

OARS maintains a modest fleet that comprises five known aircraft, made up of McDonnell Douglas DC-10 and Boeing 707 airframes, of which four are currently active. This includes one DC-10-10-40 (designated by OARS as KDC-10A), one DC-10-30 (KDC-10B), and two 707-300s (KC-707s). A further KDC-10B is currently in storage.

 

Table 1: Specifications of Omega Air Refuelling Services’ Tankers
Aircraft Type	AAR configuration	Maximum offloadable fuel	Maximum fuel offload rate	Notes
KDC-10A	2x Eaton 909E wing-mounted hose/drogue pods	53,534kg (based on a 5-hour mission)	1,215kg/min
KDC-10B	McDonnell Douglas flying boom (extendable to 17 metres)	71,810kg (based on a 4-hour mission)	2,270kg/min	Two aircraft acquired from the Royal Netherlands Air Force in 2019.
KC-707	2x Sargent Fletcher FR300T wing-mounted hose/drogue pods	35,473kg (based on a 5-hour mission)	~1,500kg/min

 

OARS’ capabilities (see Table 1) are largely comparable to modern military-operated tankers, including the A330 MRTT and the KC-46A Pegasus. The KC-46 carries approximately 96,162 kg of fuel, which can be offloaded via the boom at its maximum capacity at a rate of 4,500 kg/min and through its hose and drogue wingtip pods at 1,500 kg/min. Meanwhile, the A330MRTT can carry 111,000kg of fuel, which can be offloaded at rates of around 2,725 kg/min via the boom and 1,300 kg/min via the hose/drogue system.

As such, while OARS does not use aircraft that are currently operated by NATO militaries, they remain a capable supplement that largely matches the capacity and offload capabilities of the most relevant contemporary tankers. Moreover, the NATO Joint Air Power Competence Centre’s (JAPCC) tanker/receiver clearance matrix reveals that OARS’ tankers are compatible with a large quantity of NATO receiver aircraft, including those from Canada, Finland, Greece, Poland, Portugal, Romania, and Spain.

Many of these operators lack their own tanker capabilities or are not part of NATO’s MMU. This level of compatibility, then, highlights how Omega, and COCO AAR more broadly, aligns with the capabilities of its military counterparts, and could easily offer additional flexibility for operators with limited resources.

For some European air forces, AAR is less central to doctrine, particularly where a country’s geography means their expected operations fall within the natural, unrefuelled range of their aircraft. However, potential conflicts are unlikely to be so localised. As such, neglecting AAR training is not a viable option, otherwise threatening to undermine their interoperability with coalition partners, a cornerstone of NATO’s overall ability to respond to multiple threats or crises simultaneously. COCO tankers, therefore, provide a pragmatic means for these operators to sustain interoperability without overburdening limited sovereign resources.

Metrea Strategic Mobility

MSM entered the market in 2020, following the acquisition of four KC-135R Stratotankers from the Republic of Singapore Air Force. These aircraft were transferred directly from operational services, offering an immediate AAR capability. In July 2024, MSM expanded its fleet by adding 14 KC-135FR and KC-135RG Stratotankers from France, bringing its total to 18.

MSM’s significance lies in its interoperability with US and NATO assets, which continue to rely heavily on the KC-135 for AAR, with 376 still in active service. Among these, 17 aircraft are permanently based in the UK, while continuous rotations of US-based aircraft to Poland and Germany further augment NATO AAR requirements, significantly increasing the likelihood of NATO crews encountering a KC-135 during operations.

 

MSM’s aircraft retain all the KC-135’s unique configurations, including the Multi-Point Refuelling System (MPRS) and Boom-Drogue Adapter (BDA) systems, which support hose and drogue refuelling (for more detailed specifications, see: ‘Fuelling the future fight: Inside the USAF’s 100th Air Refuelling Wing’ in ESD 07/08-25). These capabilities, however, are scarce. Only 20 US KC-135s have the MPRS, with only four permanently assigned to Europe; BDA fitting is mission dependent, meaning consistent access to these capabilities for training is not always guaranteed.

However, for NATO aircrews, exposure to these systems is essential, as the likelihood of encountering a KC-135 operationally remains high for both boom and hose/drogue receivers. Thus, growing operational commitments threaten the availability of training on USAF aircraft. For MSM, Morgan explained that this means the company’s goal is to “fly as closely to a USAF KC-135 as they will allow us to do.” MSM’s tankers are thus highly valuable, offering a like-for-like capability that enables crews to train using capabilities and standards that mirror real-world operations without expending operationally essential tankers. Morgan attested that “to this date, [MSM is] able to do that.”

COCO AAR: Scope to grow, not a panacea

The commercial AAR sector now represents a key force multiplier, with growing interoperability between a broad array of receivers. However, after AAR was identified as a key shortfall in Europe by the European Defence Agency in 2013, a 2014 report by the JAPCC, ‘Air-to-Air Refuelling Consolidation: An Update’, revealed that despite recommendations to leverage COCO AAR, and subsidised compatibility trials offered by OARS, no EU Member State took advantage of this opportunity that year.

Over a decade later, receiver-capable aircraft inventories continue to expand faster than tanker fleets – particularly boom receivers. As such, OARS and MSM’s growing provision of boom-equipped tankers should be looked toward to assist in closing this gap. This is particularly relevant to the UK, where Voyager is increasingly incompatible with its modern fleets, notably the RAF’s RC-135W Rivet Joints, for which it currently relies on US KC-135s for refuelling, while the future F-35A’s incoming nuclear capability risks becoming undermined by a lack of compatible sovereign AAR capability.

Germany’s successful uses of COCO AAR demonstrate the missed opportunities of the past and COCO AAR’s growing current promise, operating effectively alongside NATO’s MMU, reducing strain on its high operational tempo. As the US Air Force begins to view commercial refuelling as an essential, long-term component of operations, Europe should, at the very least, begin to assess its potential benefits there.

Integrating COCO AAR with military assets solutions would help address any future NATO tanker shortages proactively by alleviating pressure on scarce resources. While not an effective replacement for dedicated national fleets, COCO AAR can help sustain everyday tanker operations, especially in smaller states that cannot afford an independent capability and/or do not require as frequent AAR training. This will serve to maintain NATO’s interoperability, while bolstering capacity to project air power without overburdening strained sovereign assets.

Luca Chadwick