Reserve Requirements Push Electric Regional Aircraft Toward Hybrid Designs

Anders Forslund presents Heart Aerospace’s central design choice as a response to a constraint that batteries do not solve on their own: an airliner must carry enough energy not only for its planned route, but also for delays and diversions.

He describes diversion capability as the company’s hardest problem, rather than the motor or battery itself. About one in every thousand U.S. flights is diverted to another airport, he says. An aircraft may need 45 minutes of loiter time and then enough range to reach an alternate airport as far as 100 miles away. Jet fuel becomes lighter as it is burned; a battery does not. In Heart’s calculation, a fully battery-electric aircraft would need to devote roughly two-thirds of its battery capacity to reserves.

Heart’s answer is a hybrid architecture: battery-electric operation on shorter missions, with a simple turboprop engine for longer operational range and contingency coverage. Forslund says the engine adds roughly 20% to the upfront cost of the aircraft, but regards that as worthwhile because it avoids the reserve burden of a battery-only design.

The company’s planned ES-30 is intended to fly up to 125 miles on battery power alone and up to 500 miles with the hybrid system. Heart describes a recharge time of about 30 minutes. The aircraft can carry up to 36 passengers, though Forslund expects 30 seats to be the common configuration, leaving each passenger about six additional inches of legroom.

The X1 demonstrator that has now flown has a 100-foot wingspan and a 25,000-pound takeoff weight. Heart characterizes it as the world’s largest electric aircraft to fly; Forslund puts it at about twice the scale of the next-largest electric aircraft. He also calls it the first clean-sheet airliner flown in the United States, in any propulsion category, in 18 years.

Heart describes itself as a hybrid-electric aircraft company, but Forslund’s stated mission is broader: reducing the cost of air travel by building the technologies that enable it. The hybrid system is the mechanism meant to make that ambition compatible with present-day airline operating requirements rather than contingent on eliminating them.

The case for the aircraft begins where conventional jet propulsion is least well suited, according to Anders Forslund: short regional flights.

A jet engine for a 30-seat aircraft is about as complex to build as one for a 70-seat aircraft, he argues. It costs about the same and experiences the same wear whether it flies 100 miles or 1,000. That structure pushes airlines toward larger aircraft and longer routes. Regional flights bear particularly unfavorable costs because taxiing, takeoff, and landing consume a disproportionate share of the fuel; on a short flight, Forslund says, taxiing can account for 10% of fuel use.

Electric motors offer a different cost and maintenance profile in Forslund’s account. He compares Heart’s 400-kilowatt motors with the small motors used in drones: the basic technology is the same, scaled up. The aircraft motor has very few moving parts—he describes it as essentially one—and does not depend on combustion or fluid systems. That simplicity, he argues, makes the motors cheaper to produce and leaves them with effectively zero wear relative to combustion engines.

The difference is apparent during taxiing. A jet engine produces output beyond what a taxiing aircraft needs, with the excess becoming noise. An electric motor has a constant torque profile and can turn at a fraction of its operating speed. At roughly one-tenth speed, Forslund says, it is virtually silent from 100 feet away.

Gustaf Alströmer frames the potential market as an existing one rather than a demand category that needs to be created: half of flights globally are under two hours. Forslund sees a replacement market in regional aircraft based on designs that are roughly 40 years old. Regional connectivity is not principally about the maximum distance an aircraft can travel, he argues, but about the cost of operating the route. By that standard, the shortest viable routes are especially attractive.

The examples are island hopping in Hawaii and a Norwegian fjord town where a six-hour drive could become a 20-minute flight. Forslund says Heart’s overall operating-economics advantage improved from 33% to 48% over the preceding year because of increased oil prices.

The company’s battery packs are laid across the X1’s fuselage floor. Forslund describes the eight packs as equivalent to about four Teslas and says the energy carried amounts to approximately $40 worth of fuel. The point is not merely that electricity reduces emissions; it is that the cost of propulsion can favor the routes for which jet engines impose the greatest relative burden.

Heart’s Los Angeles pilot plant treats battery integration as a design problem with competing requirements: flight-cycle life, safety, cost, and energy density. The battery lab holds cells from Chinese, American, and Korean manufacturers for comparison against those criteria.

A technical display identifies Heart’s “X2 POR CELL” as an Amprius SA-11 and gives the following specifications.

Forslund connects the work to a moment at MIT 12 years earlier, when he heard Elon Musk discuss electric aircraft and batteries reaching 400 watt-hours per kilogram. At the time, Forslund was working on jet engines during the day and experimenting with drones at his kitchen table at night. The prospect of batteries at that energy density made electric aviation feel like a feasible direction rather than a distant thought.

In the lab, he asks whether Heart has cells at 400 Wh/kg. A team member says the highest cells on the table are around 370 Wh/kg. One manufacturer is producing a cell at around the 400 Wh/kg level that Heart expects to have within the next few months, the team member says, and that cell would meet the targets for the aircraft’s first generation.

The hybrid approach is also Heart’s answer to the question of why it is not pursuing hydrogen. Forslund argues that hybrid electric is already operating with a “significant” negative green premium: it can be less expensive while also reducing emissions. In his view, that lets Heart build on an improving battery and electric-powertrain base instead of depending on a separate fuel and infrastructure transition.

Heart began with airline interest before it had the technology to build an aircraft. Anders Forslund had been researching electric aviation while working on jet engines, and had been paid by the Swedish government to speak with Nordic airlines before forming the company. Those conversations established relationships that later became early commercial signals.

At Y Combinator, the company arrived with a 3D-printed plane small enough to hold in one hand. Forslund and co-founder Klara secured letters of intent from SAS, Braathens, and Widerøe despite, as Forslund puts it, having “really no technology.” The next task was to turn that interest into a concrete technical demonstration: a 400-kilowatt electric motor, approximately the size of the small jet engine Heart wanted to replace.

That physical artifact helped attract pre-orders, including from United Airlines, and then capital to continue building toward the aircraft. United’s initial contact came through the company’s general inbound email address. Forslund says Klara found the message while clearing spam, decided it might be real, and brought the airline in to see the motor. Seeing an electric motor built at the scale of the jet engine it was intended to replace made the proposition immediately comprehensible, he says.

The progression informs Forslund’s advice to hardware founders. Each time a company needs more capital, it should be able to show something material that it has made—ideally something a prospective customer or investor can touch.

The aircraft itself was deliberately designed to look conventional. Many electric-aircraft startups opt for visibly futuristic designs; Heart chose an aircraft that resembles the turboprops it aims to replace. Forslund says the company is not trying to build a sports car. His preference is for something conventional-looking that hides its “Superman cape under the hood.”

The contrast between the first model and the aircraft shown on the runway is central to Heart’s account of its seven-year development. Forslund recalls arriving at YC with the small 3D-printed model; the X1 is now a 100-foot-wingspan aircraft. The source identifies its first flight at Plattsburgh International Airport.

Heart’s Los Angeles pilot plant is intended as an in-house development environment where aircraft systems can be built, instrumented, broken, and tested without waiting on the conventional aerospace supply chain.

A team member displays an actuator cylinder body machined from 6061 aerospace aluminum. The actuator contains roughly 15 machined components, and Heart is developing the associated manufacturing processes internally. In traditional aerospace, Anders Forslund says, the component would be sourced from a supplier and could take a year to arrive. Producing it in-house lets engineers experiment with it and test it directly.

Heart is applying that approach across common actuator architecture: ailerons, rudders, landing-gear extension, brakes, and propeller pitch. Forslund’s test for deciding what to bring inside the company is whether a system otherwise requires coordinating many supplier technologies. Building shared underlying technologies internally, he argues, lets complexity scale with the number of technologies rather than the number of suppliers.

The plant is wired as a large test bench. Forslund describes being able to separate the aircraft into major sections—the cockpit, cabin, and tail—and test them under 1.6 megawatts of supplied power, which he says would be enough to keep the aircraft airborne. The plan includes fault injection: introducing programming errors, cutting wires, and testing whether the system continues to work when components fail.

That approach reflects his view of development risk. Traditional aerospace, Forslund says, begins with the assumption that the impact of failure is catastrophic and so tries to minimize the probability of error before moving forward. Heart instead aims to reduce the impact of being wrong, allowing cheaper and faster iteration. Planes do not crash because of broken wings, he argues, but because of “broken logic.” The intended vehicle is therefore software-defined: “a computer on wings.”

Heart distinguishes its market from electric vertical-takeoff-and-landing businesses. Anders Forslund calls those efforts “super cool,” but characterizes them as attempts to build something closer to a flying car. Heart is targeting the mainline airplane market rather than the helicopter market: an aircraft carrying up to 36 passengers rather than three or four, operating through airport infrastructure that is already in place. Alströmer says the United States has 5,000 airports.

The company’s economic case depends on serving regional routes at lower cost, not on creating an entirely new aviation-infrastructure category. Forslund says quieter propulsion and lower vibration could accompany more frequent service and cheaper tickets, allowing travelers to use neighborhood airports in a way he says was more common in the past.

Forslund sees the 36-seat aircraft as a starting point rather than a ceiling. Heart would like to build bigger planes, he says, and he identifies narrow-body aircraft such as the Boeing 737 and Airbus A320 as the larger market, citing what he calls their “ridiculous backlogs.”

He also describes a longer operational progression: remote pilots supporting multiple aircraft, analogous to remote operators at Waymo; autonomy first in cargo, where he says the stakes are lower; and only later, potentially, in passenger aircraft. That future remains separate from the immediate proposition: making a regional aircraft useful within today’s airport network.