Between September and October 2025, Airbus and several partner airlines quietly carried out a series of transatlantic test flights. The aim was bold: prove that two long-haul aircraft can be guided to meet at precisely the same point in the sky, at the same time, without breaking a single air traffic control rule. That rendezvous is the missing step before a new way of flying that could cut fuel burn by up to 5% on long routes.
From theory to sky: a world first for wake energy flights
The project, called fello’fly, is built on a simple, almost poetic idea borrowed from nature. Migrating birds, such as geese, fly in formation to share the aerodynamic load. One bird rides in the gentle upwash created by the wingtips of the leader, using less energy, then takes its turn at the front.
Airbus wants to adapt that strategy to modern jets. In technical terms, the concept is known as “wake energy retrieval”: one aircraft positions itself in the updraft created by the wingtip vortices of another, slightly ahead. That extra lift lets the trailing aircraft reduce engine thrust while maintaining speed and altitude.
Engineers estimate that once operational, wake energy flights could trim fuel use on long-haul services by around 5% per trip.
For an industry already under pressure over its climate impact, that is not trivial. Aviation is responsible for roughly 2–3% of global CO₂ emissions, and most of that comes from long-haul flights. Shaving a few percentage points off every crossing translates into thousands of tonnes of kerosene saved each year.
The breakthrough announced now does not yet involve full formation flying. What Airbus has validated is a precursor: the ability to choreograph two independent commercial flights so that they converge with metre-level precision at a shared rendezvous point, fully within existing safety rules and air traffic procedures.
Eight transatlantic tests, one very tight rendezvous window
A multinational rehearsal above the North Atlantic
The campaign involved eight flights over the North Atlantic, one of the busiest and most tightly regulated oceanic airspaces in the world. Airbus teamed up with Air France, Delta Air Lines, French bee and Virgin Atlantic to provide aircraft and crews.
On the ground, several air navigation service providers joined the experiment: AirNav Ireland, the French provider DSNA, UK-based NATS and the pan-European coordination body EUROCONTROL. Each organisation had its own procedures, software and legal obligations, which made the exercise almost as much an organisational challenge as a technical one.
Engineers compare the situation to two cyclists climbing the same mountain pass while speaking to different team cars on separate radios. A tiny change in speed or wind can shift the meeting point by miles. Matching their positions still requires both support cars to constantly recalculate, adjust tactics and sign off on each move.
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Behind the scenes, every adjustment to heading, speed or altitude passed through air traffic control checks before pilots were cleared to act.
For the crews, the flights added a new layer of cockpit routine. Instead of simply following a pre-filed route, they had to interact with an Airbus-developed system called the Pairing Assistance Tool, or PAT.
How the pairing assistance tool guides two jets together
The PAT runs in real time, ingesting flight plans, winds, aircraft performance data and constraints from air traffic control. It then proposes rendezvous points and the trajectory changes needed for each aircraft to arrive at exactly the same place at a specified time.
The test protocol followed four main stages:
- Dynamic calculation: PAT computes adjusted trajectories for both aircraft based on their current positions and expected conditions.
- Joint validation: Airlines, flight crews and controllers check whether those trajectories respect safety margins, regulations and workload limits.
- Plan update: One aircraft adjusts its flight plan, with controller approval, to move towards the rendezvous point.
- Pilot commitment: Both crews deliberately activate a cockpit function that “locks in” the time and place of the meeting, triggering the aircraft systems to guide them there.
The core challenge lies in accuracy. The rendezvous must be close enough that, in future, the following aircraft can slip into the upwash zone created by the lead aircraft’s wingtips. At the same time, the planes must respect existing separation minima up until the moment regulators approve formation flight procedures.
Borrowing from geese to cut emissions
The physics behind wake energy retrieval
For many passengers, the idea of flying one large jet in the disturbed air of another may sound counterintuitive. Yet the physics underpinning the concept are well documented. As an aircraft wing generates lift, it sheds swirling air masses called vortices at each wingtip. Just outside those vortices, a band of air rises gently.
If a second aircraft positions itself in that upwash, slightly behind and offset from the leader, it needs less lift from its own wings and can reduce thrust. Cyclists feel something similar when they ride in the slipstream of another rider, using less energy for the same speed.
The difference in aviation is that there is no room for improvisation. Positions must be calculated precisely. Vertical separations must be safeguarded. Every move must be visible to, and accepted by, air traffic controllers who are also managing dozens of other flights.
The fello’fly trials build on earlier research, including a European project called GEESE, funded under the SESAR air traffic modernisation programme. That initiative brought in a broad pool of partners, among them Boeing, European universities, research labs and several national air navigation providers. The message is clear: no single company can change cruise flight operations on its own.
From demonstration to daily operations
At this stage, none of the test flights actually flew in close formation to harvest the wake energy. The objective was narrower: confirm that two scheduled flights, operated by different carriers, can be paired, sequenced and brought together in a predictable, safe way.
The next phase will move closer to the birds. Once regulators and safety experts are satisfied, Airbus wants to run trials where the trailing aircraft truly settles into the sweet spot of the leading aircraft’s wake and maintains that position long enough to measure fuel savings in realistic conditions.
| Aspect | Traditional cruise | Future wake energy flight |
|---|---|---|
| Aircraft separation | Fixed lateral and vertical spacing | Closer, controlled formation within defined corridors |
| Fuel use | Based solely on own lift and thrust | Trailing aircraft benefits from upwash, reducing thrust |
| Route planning | Individual optimised routes | Coordinated pair planning with shared rendezvous |
| ATC workload | Standard procedures | Additional coordination tools and joint decision-making |
Part of a wider climate strategy for aviation
Fello’fly among many levers
Wake energy retrieval sits alongside a wider range of efforts to shrink aviation’s climate footprint. Airlines are already trialling sustainable aviation fuels (SAF), made from feedstocks such as waste oils or captured CO₂ combined with green hydrogen. Across their full life cycle, some of these fuels can cut emissions by up to 80% compared with conventional kerosene, depending on how they are produced.
Engine makers are also pushing high-bypass turbofans and new core designs that squeeze more efficiency out of every kilogram of fuel. Aircraft structures continue to get lighter thanks to advanced composites, new alloys and clever cabin layouts that trim unnecessary weight.
Alongside this, smaller electric and hybrid-electric aircraft are advancing for regional routes, while several companies look at battery-assisted or hydrogen-powered concepts for short hops. For longer distances, hydrogen could be burned directly in modified turbines or fed into fuel cells that power electric motors.
Each of these avenues addresses a different piece of the climate puzzle; none is sufficient alone, but together they shift the trajectory of the sector.
What formation flying would mean in practice
Passenger experience, benefits and risks
If fello’fly reaches routine use, long-haul travellers crossing the Atlantic might one day be flying in loose formation without realising it. From a window seat, the only clue could be the distant silhouette of another widebody cruising a few miles ahead and to the side, rather than on a completely separate track.
From an airline’s perspective, a 5% fuel reduction on a large twin-aisle aircraft can mean several tonnes of fuel saved on a single trip. Over a year, on a busy transatlantic route, that adds up to millions of dollars in costs avoided and a significant cut in CO₂ emissions.
The approach does introduce new forms of risk that regulators will pore over. Controllers must avoid creating extra complexity in already dense oceanic corridors. Crews will need specific training to understand formation geometry, wake behaviour and new cockpit modes. Robust rules will be needed to handle unexpected events: a sudden diversion, medical emergency, turbulence, or a technical fault on one aircraft while in paired flight.
Key concepts worth understanding
A few terms are likely to surface more often as formation-efficient flying advances:
- Wake turbulence: The disturbed air, especially wingtip vortices, left behind by an aircraft. It can be uncomfortable or dangerous for smaller aircraft that cross it unintentionally, which is why strict separation rules exist today.
- Upwash zone: The region of air lifted gently upwards just outside the core of those vortices. That is where a following aircraft in fello’fly would aim to position itself.
- Separation minima: The regulated minimum distance between aircraft, measured vertically and horizontally, designed to keep wake effects and collision risks under control.
- Oceanic control: Air traffic management over the sea, usually based on satellite and long-range communications, where radar coverage is limited and tracks are planned well in advance.
As satellites, onboard sensors and data links improve, the precision with which aircraft can be guided through these invisible structures in the sky will increase. Fello’fly’s latest milestone shows that aligning two widebody jets at a shared rendezvous in real traffic is no longer just a PowerPoint concept, but a manoeuvre that real crews can execute under real constraints.
If regulators eventually greenlight formation cruise, wake energy retrieval might sit alongside sustainable fuels, new engines and alternative propulsion as one more practical lever to make long-haul flying less fuel hungry than it is today.