Delta Air Lines explores goose-like formation flying to save fuel

Delta Air Lines has announced plans to test a fuel-saving tactic inspired by the V-shaped formation used by migrating geese. The approach, known as Wake Energy Retrieval (WER), has the potential to cut fuel use on long-haul flights by 5 percent, a significant saving for an industry seen as one of the hardest to decarbonize. 

“When you can get potentially 5 percent fuel efficiency gains for wide-body aircraft when there’s not an immense amount of other solutions, that’s really compelling,” said Amelia DeLuca, Delta’s chief sustainability officer.

The biomimicry approach, dubbed fello-fly and pioneered by aircraft manufacturer Airbus, was the subject of a successful trans-Atlantic test in 2021, when a pair of empty A350s flew between Toulouse, France and Montreal, Canada. Delta is aiming to test WER on a regular trans-Atlantic passenger flight, likely in the fourth quarter of this year. The test could involve a pair of aircraft operated by Delta, or one provided by other partners in the program, which include Virgin Atlantic and Air France, said DeLuca.

How it works

The fuel savings occur when the plane at the back of the pair surfs the uplift from the wake of swirling air created by the leading plane. To do so, the follower must cruise relatively close to the leader — around 1.4 miles is the optimal separation for fuel saving. Aircraft in oceanic airspace typically fly at least 30 miles apart, but smaller distances are common in other situations. One thousand feet of vertical separation is the closest allowed by safety regulations.

With the fuel-saving potential demonstrated in earlier tests, the challenge is to figure out how the many stakeholders and technologies can be coordinated to make WER flights routine. Planes that pair for a trans-Atlantic flight must be directed by air traffic control to a rendezvous point, where they maneuver into position. The craft must then stay as close as possible to the optimal distance until they separate for landing, a process handled by onboard technology. DeLuca likens the system to Tesla’s autopilot, which will automatically brake if the car comes within a pre-defined distance of the vehicle in front of it.

‘Do it slowly’ is the mantra

The emphasis that the industry places on safety, as well as the many parties involved, explains why it has taken five years to move from initial tests to commercial trials, added DeLuca, who said it was too early to say when use of WER could become routine. “Part of sustainability that we always talk about on my team is this mantra of do it slowly, so that it exists decades to come, instead of forcing it through and then having something go wrong and then, of course, we wouldn’t use it,” said DeLuca.

To an outsider, a 5 percent saving may not seem notable given aviation generates around a billion tons of carbon dioxide annually. But it’s a significant opportunity for an industry that lacks scalable and affordable alternatives to fossil fuels. Battery-powered aircraft, for example, are only suitable for short flights. Sustainable aviation fuel (SAF) can be a direct substitute for jet fuel, but there is not enough suitable biomass available to scale production to meet global fuel demand.

SAF is also significantly more expensive than jet fuel, whereas WER can save airlines money. “We regularly do business cases that if you can get half a percentage of fuel efficiency, that has a payback of under two years, because fuel is such a cost burden for us,” said DeLuca. “You think about when we drop a winglet on a plane, it’s usually less than 1 percent and we still regularly are putting winglets onto our flights. So it’s good business sense.”

The WER tests are also an example of Delta’s role in the innovation ecosystem, DeLuca added. “It speaks to what Delta believes our role is more broadly in unlocking some of these solutions,” she said. “We are not the ones necessarily that need to be on the forefront of R & D. There’s great universities that you know will do that work. When the innovation is ready to be tested, Delta will be there with our operation, with the power of our people to do that work.”

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