Heart Aerospace, the ES-Thirty, and the Battery Math That Made a Swedish Startup Tear Up Its First Design and Start Over

Heart Aerospace’s pivot from the all-electric ES-19 to the hybrid-electric ES-30 is one of the most consequential - and honest - engineering decisions in modern regional aviation. Battery energy density didn’t improve fast enough to make a 19-seat, 250-mile pure-electric regional aircraft commercially viable on the routes that mattered. So the Swedish startup tore up the design and built a better one.

Why Regional Aviation Lost Hundreds of Short-Haul Routes

Over the past two decades, U.S. regional aviation shed hundreds of short-haul routes - the 100-to-400-mile hops that once connected mid-size cities to their nearest hub without a three-hour drive. These routes didn’t disappear because demand vanished. They died because the economics of small turboprop operations became permanently unfavorable: fuel burn per seat-mile is high, maintenance costs are disproportionate, and crew costs don’t scale down the way passenger count does.

The airports that served these communities have seen their infrastructure decay for lack of revenue to maintain it. The market gap Heart Aerospace was founded to fill is real, documented, and measurable in the network maps of every major U.S. carrier.

Heart Aerospace’s Original Thesis

Heart Aerospace was founded in 2018 by Anders Forslund in Gothenburg, Sweden. Forslund’s core thesis: battery technology was improving steadily, electric motors were demonstrably more efficient than combustion engines at small scales, and regional aviation was the first commercial segment where those two improvement curves would intersect. Short-haul commuter flights have low enough energy requirements that batteries could plausibly cover them before they could cover anything larger.

The company’s first aircraft, the ES-19, was a clean-sheet, 19-seat, fully electric regional aircraft designed for 250 miles of range on battery power alone. The projected operating economics would, if the projections held, undercut any competing turboprop flying those routes today.

The Investor Validation That Preceded the Pivot

In 2021, the ES-19 attracted serious institutional backing. United Airlines invested $50 million in Heart Aerospace. Air Canada made a strategic investment around the same time. Mesa Air, which operates regional services under the United brand, signed a purchase agreement for 240 aircraft - not a letter of intent, but an order grounded in route analysis on actual underserved markets that United’s network planners had identified as commercially viable with the right aircraft.

That level of validation is something most aviation startups never reach.

Why Heart Abandoned the ES-19 in 2022

In 2022, Heart announced it was abandoning the ES-19 and published a technical briefing explaining the decision in unusual detail.

The problem was battery energy density. Aviation-grade jet fuel delivers approximately 12,000 watt-hours of energy per kilogram. A lithium battery pack in a certified aircraft application delivers somewhere between 250 and 300 Wh/kg - once you account for packaging, thermal management systems, and required safety margins. Electric motors are more efficient than turbines, which helps close the gap. But even with that efficiency advantage, the energy storage density gap between batteries and fuel runs roughly four-to-one in favor of fuel.

For a 19-seat aircraft doing 250 miles, this means a battery pack that constitutes a significant fraction of maximum takeoff weight. When Heart’s engineers modeled the 13 specific United Airlines regional routes their investors needed covered, the pure-electric design left gaps that the battery technology timeline couldn’t close: routes slightly too long, payloads that stressed the margins, weather diversions that consumed the reserve.

Forslund and the Heart team faced a choice most startups navigate badly. They could have pushed forward, argued that battery chemistry would arrive on schedule, and hoped. Instead, they went back to their investors and said: the design doesn’t work. Here’s a new one.

The ES-30: What Changed and Why It Matters

The ES-30 is a 30-passenger hybrid-electric regional aircraft. The seat count increase from 19 to 30 is not cosmetic - 30 seats hits a different commercial sweet spot, serving routes too thin for a 50-seat regional jet but generating enough demand to be profitable at that scale.

The fundamental engineering change is in propulsion. The ES-30 carries a battery pack that handles the highest-power phases of flight: takeoff, initial climb, approach, and landing. These are the phases where conventional aircraft burn the most fuel per minute and where electric motors have the greatest efficiency advantage. They are also where airport noise matters most to surrounding communities, and electric propulsion substantially reduces that noise signature.

For cruise, the ES-30 uses two small turbogenerators - compact turbine engines whose sole job is generating electricity, not driving the aircraft directly. The electric motors on the propellers handle all propulsion. The turbogenerators run on sustainable aviation fuel (SAF) or conventional jet fuel when SAF isn’t available, and they operate at a constant, optimized power setting regardless of flight demand - meaningfully more efficient than a conventional engine modulating power across a wide range of conditions.

The result is a pure-electric range of approximately 200 miles and an extended range of roughly 400 miles with the turbogenerators running.

The Propulsion Architecture Most People Miss

Heart is using a distributed electric propulsion layout - multiple electric motors driving the propellers, providing redundancy that a conventional twin-engine design cannot match. If one motor degrades or fails, the others continue operating. The flight management system monitors each motor independently and redistributes power in real time. That kind of fault tolerance is structurally difficult to achieve with mechanical propulsion and represents one of electric drive’s genuine structural advantages in aviation.

The battery pack is integrated into the aircraft structure from the initial design, sitting in the lower fuselage and functioning as a structural component rather than an add-on. This is categorically different from electric propulsion retrofits on existing airframes, where batteries fight the original weight and balance assumptions. Heart’s approach adds certification complexity - qualifying the battery as both an energy storage system and a structural element - but it optimizes the overall vehicle rather than compromising it.

The charging architecture is deliberately conventional. The ES-30 is designed to use standard ground power connections that most regional airports already have, supplemented by turbogenerator capability for routes where charging time is limited. One of the adoption risks with pure-electric aircraft is the infrastructure investment required at every destination before a route can open. The ES-30 substantially reduces that dependency.

The Competitive Landscape

Heart is not operating in isolation. Eviation’s Alice, a 9-seat all-electric commuter aircraft, completed its first flight in September 2022, targeting routes under 100 miles where pure-electric range is adequate. Eviation has had setbacks - including a battery thermal event during ground testing - but the aircraft exists as a flying machine, not a rendering.

The established regional manufacturers are watching closely. ATR has an internal hybrid-electric development program. De Havilland Canada has explored electric variants of the Dash 8 platform. These companies carry significant advantages in certification experience, supplier relationships, and the service networks that airlines need to actually operate an aircraft type commercially. They move more slowly than startups. Whether they move quickly enough to capture the market before Heart does is one of the more genuinely open competitive questions in aviation right now.

The SAF supply chain deserves separate mention. The ES-30’s turbogenerators are designed to run on SAF, which remains constrained at most airports. Heart has been transparent that conventional jet fuel works equally well - the pragmatic hedge that means the aircraft operates regardless of SAF availability, with a smaller emissions reduction advantage if supply chains don’t develop as major producers project.

Certification Path and Timeline

Heart is pursuing type certification through EASA (European Union Aviation Safety Agency) as primary certification authority, with FAA validation planned for the American market. The EASA pathway under commuter category aircraft rules is rigorous but substantially less burdensome than full airliner certification.

The current projected schedule calls for a technology demonstrator flying in 2026 and entry into service in approximately 2028 or 2029. These dates have moved from earlier projections, attributed to supplier qualification work, regulatory alignment, and standard engineering refinement as a design transitions from concept to physical hardware.

A timeline slip is not inherently a technical failure - the question is always what caused it. Heart’s published technical updates have been consistent: the ES-30’s architecture has been stable since the 2022 pivot. The delays are in integration and qualification work, not in the underlying physics. That is a categorically different situation from a slip driven by discovering the core design doesn’t work.

Why This Matters for Pilots and the Regional Network

The routes that have disappeared from the U.S. regional network represent real connectivity losses for communities that had no alternatives. The economic model that killed those routes - high fuel burn, high maintenance, unfavorable crew-to-passenger ratios on thin markets - is precisely what hybrid-electric propulsion addresses most directly.

United Airlines’ $50 million investment is not altruistic. United has been explicit that regional connectivity is a structural element of their hub-and-spoke network, and that fuel costs and crew availability are putting the regional flying economic model under pressure in ways that electric propulsion could materially address.

For pilots, a commercially viable hybrid-electric short-haul fleet means routes that don’t exist today, operating economics that support launches into underserved markets, and aircraft with maintenance profiles fundamentally different from current turboprops. Distributed electric propulsion systems and structurally integrated battery packs will require new training, new maintenance certifications, and a rethinking of systems knowledge that pilots currently carry as standard.

Key Takeaways

Heart Aerospace abandoned its 19-seat, all-electric ES-19 in 2022 after battery energy density failed to meet real-world route requirements - a rare act of public engineering honesty from a well-funded startup.
The replacement ES-30 is a 30-seat hybrid-electric aircraft that uses batteries for high-power flight phases and turbogenerators for cruise, yielding a pure-electric range of ~200 miles and an extended range of ~400 miles.
United Airlines ($50M investment), Air Canada, and Mesa Air (240-aircraft order) made real financial commitments based on identified underserved routes in existing hub networks - not speculative bets on press releases.
The ES-30’s distributed electric propulsion and structurally integrated battery pack are genuine architectural advantages over retrofitted electric designs, at the cost of increased EASA certification complexity.
The current timeline targets a technology demonstrator in 2026 and entry into service around 2028-2029 - aggressive but grounded in a design architecture that has been stable since the 2022 pivot.