In late 2025, Airbus and several partner airlines conducted a series of test flights that proved something long considered almost impossible: bringing two large commercial aircraft to the exact same point in space and time, under normal air traffic control rules, without compromising safety.
From bird formations to jetliners: a radical idea takes shape
The project, known as fello’fly, borrows directly from the way migratory birds travel in V-shaped formations. When geese fly in formation, those behind benefit from the air flow created by the leader. Airbus wants to do roughly the same with airliners cruising across oceans.
The core concept is called “wake energy retrieval”. Every aircraft leaves behind a complex pattern of air, including upward-moving vortices generated at the wingtips. If another aircraft positions itself in just the right spot, it can get a small aerodynamic boost, requiring less engine thrust and burning less fuel.
Airbus estimates that mature wake energy retrieval operations could cut fuel burn on long-haul routes by up to 5% per flight.
That may sound modest, but on heavily travelled transatlantic corridors, a 5% cut means thousands of tonnes of jet fuel saved every year. For an industry under pressure to curb emissions, this kind of gain, achieved without new engines or radically different aircraft, looks very attractive.
The historic rendezvous over the Atlantic
Between September and October 2025, Airbus oversaw eight test flights over the North Atlantic. These were not abstract simulations. They involved real aircraft, real crews, real passengers, and real air traffic controllers in Ireland, France, the UK and within the EUROCONTROL network.
Multiple airlines took part in the campaign, including:
- Air France
- Delta Air Lines
- French bee
- Virgin Atlantic
The challenge was not simply to fly two jets close together. Strict separation rules still applied. What the teams set out to verify was whether two independent commercial flights could be guided so precisely that they reached the same rendezvous point, at the same altitude layer and at the same moment, while remaining fully compliant with existing safety procedures.
Think of two cyclists climbing a mountain from different valleys, each following instructions from separate team cars, yet still reaching the same bend within seconds of each other.
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Any small deviation in speed, wind, or route required fresh calculations. That made the tests as much a demonstration of coordination and decision-making as of aerodynamics.
The digital co-pilot: pairing assistance tool
How the rendezvous actually works
At the heart of the operation sits the Pairing Assistance Tool (PAT), software developed by Airbus to act like a high-precision, future-looking GPS for aircraft pairing.
The trials followed a strict four-step protocol:
What makes this method notable is not just the precision; it is the insistence on voluntary human action at every stage. The tool suggests routes, but pilots and controllers remain firmly in charge.
| Aspect | Current status |
|---|---|
| Common rendezvous point | Validated in real operations |
| Airspace safety rules | Respected using existing separation standards |
| Wake energy retrieval itself | Next phase of testing |
| Use on commercial flights | Still under development and regulatory review |
Safety first: coordinating controllers, airlines and crews
The rendezvous tests required an unusually high level of coordination on the ground. Air navigation service providers from Ireland (AirNav Ireland), France (DSNA), the UK (NATS) and the pan-European body EUROCONTROL worked together via dedicated interfaces.
Every route change proposed by PAT had to be checked against normal traffic flows, military zones, weather deviations and sector capacity. Controllers needed to maintain standard vertical separation while bringing the aircraft into a position where a future formation segment would become possible.
The breakthrough lies in proving that this pairing can be done under routine air traffic conditions, not in a special bubble of protected airspace.
For flight crews, the concept introduced a new “ritual”. Pilots had to interpret system suggestions, liaise more closely with dispatch teams, and coordinate with a partner aircraft they might never actually see out of the cockpit windows, especially at night or in cloud.
From theory to gradual reality
The current phase: practicing the rendezvous only
Crucially, none of the test flights actually flew in full wake-benefit formation. The goal at this stage was to perfect the rendezvous and verify that two independent flights can meet safely and reliably.
The situation is a bit like testing how to align train cars on the same track without yet coupling them. The hard part is making sure they end up in the right place, at the right time, without disrupting everyone else’s timetable.
The next step will be to bring the trailing aircraft into the precise sweet spot of the wake, where upward-moving air provides extra lift. Engineers will then measure fuel savings, engine loads and any potential comfort issues, such as turbulence felt in the cabin.
Why 5% matters so much
Commercial aviation accounts for roughly 2–3% of global CO₂ emissions, and long-haul flights represent a large share of that total. On a single intercontinental route, a widebody aircraft can burn several tens of tonnes of fuel.
A 5% reduction on a single transatlantic flight might save around one to two tonnes of fuel, depending on aircraft type and route. Multiply that by daily flights and then by a full year, and the numbers begin to approach the kind of savings airlines and regulators care about.
Wake energy retrieval acts as a form of “free performance upgrade” for existing aircraft, gained through smarter operations rather than new hardware.
Fello’fly among a mosaic of green aviation solutions
Fello’fly does not stand alone. It slots into a broader strategy where the aviation sector tests multiple technologies in parallel, each solving part of the climate challenge.
Some of the main strands include:
- Sustainable aviation fuels (SAF): Drop-in fuels made from waste, biomass or synthetic processes that can cut lifecycle emissions by up to around 80% compared with conventional kerosene.
- New engine generations: Higher bypass turbofans, geared architectures and improved materials reduce fuel burn per seat on new aircraft types.
- Lighter airframes: Wider use of composites, redesigned cabins and more efficient systems shave kilograms off every flight.
- Electric and hybrid projects: Smaller regional aircraft and urban air mobility concepts using batteries or hybrid systems for short routes.
- Hydrogen research: Both combustion in modified turbines and fuel cells are being studied for future zero CO₂ flight, particularly after 2035.
European programmes such as SESAR fund related projects, including GEESE, a research effort involving Airbus competitors like Boeing, research institutes such as DLR and ENAC, and air navigation providers across Europe. That underlines a key point: no single company can reshape air traffic procedures alone; regulators and competitors must agree on common frameworks.
Key concepts behind wake energy retrieval
For readers less familiar with aviation physics, a few terms sit at the heart of the fello’fly idea:
- Wake turbulence: The disturbed air behind an aircraft, including strong vortices shed from wingtips. These can be dangerous if another aircraft flies too close behind and below.
- Lift and drag: Lift keeps the aircraft in the air, while drag resists motion. Any technique that increases effective lift or reduces drag means less thrust is needed.
- Separation minima: Standard distances and vertical gaps that controllers must maintain between aircraft to prevent conflicts and unsafe encounters with wake turbulence.
In fello’fly, the trailing aircraft does not sit directly behind the leader in the “no-go” zone. Instead, it uses carefully modelled positions slightly off-centre, where upward-moving air is available but harmful turbulence is minimised. That is where precise guidance and robust modelling become critical.
What this might mean for future passengers
If the concept reaches commercial maturity, you might one day fly from London to New York in an aircraft that spends part of the cruise phase paired with another jet, a dozen nautical miles away, sitting neatly in a sweet spot of air.
From the cabin, you likely would not notice anything. The pairing manoeuvres would be gradual, managed automatically by autopilots under pilot supervision, and authorised by controllers in the background. In theory, only a glance at the moving map or a glimpse of another airliner holding a steady relative position outside the window might give it away.
Alongside that discreet choreography, airlines could advertise lower fuel use, regulators could count measurable emission reductions, and air traffic managers would gain new experience in dynamic, data-driven route optimisation.
As with any shift in procedures, there are risks to handle: pilot workload, controller complexity, potential misunderstandings between partner aircraft, and the need for global standards rather than regional experiments. Yet the 2025 trials suggest that, with the right digital tools and training, bringing two aircraft safely to the same point in the sky is no longer science fiction, but an emerging piece of everyday long-haul operations in the making.