The 787: A warning about weight

Even on conventional combustion aircraft, batteries are becoming more critical. The Boeing 787 Dreamliner uses lithium-ion batteries to start its auxiliary power unit, back up critical systems in the event of generator failure, and power flight-control electronics. Boeing chose lithium-ion batteries over the older nickel-cadmium batteries used on the 777 and 747 because lithium-ion can deliver a large burst of power quickly — exactly what’s needed to start a jet engine.

In January 2013, two 787s suffered battery fires within days of each other — one in the air over Japan, and one on the ground in Boston. All 51 delivered aircraft were grounded for four months. Boeing’s fix involved switching from an aluminum battery enclosure to a stainless steel box, adding ceramic thermal shielding between cells, and installing new ductwork to vent fumes overboard. The result added approximately 68 kg to the aircraft — enough to completely cancel out the weight savings that had made lithium-ion attractive in the first place. It was an expensive lesson in what happens when thermal protection is treated as an afterthought.

Lilium’s legacy in battery innovation for electric aviation

Fast forward to 2024, and electric aircraft company Lilium was assembling its all-electric jet outside Munich at Oberpfaffenhofen Airport. Where the 787’s battery system stored roughly 2.8 kWh to support the aircraft, Lilium’s battery system targeted 62.5 kWh — more than 20 times the energy — and served as the sole source of propulsion. The 787’s batteries are roughly the size of a car battery, delivering emergency power for seconds at a time. Lilium’s battery system was delivering a megawatt of power on demand, cycling hard on every single flight.

Lilium’s approach to thermal protection reflected an entirely different set of demands. Rather than heavy metal enclosures, Lilium used lightweight composite battery casings and distributed risk across 10 independently functioning battery packs, designed so that the failure of any single pack could not bring down the aircraft. It was a fundamentally more elegant architecture than Boeing’s containment-box approach and, critically, achieved that safety level without the weight penalty. Lilium was unable to secure the capital needed to reach commercial service and ceased operations in early 2025. 

But Lilium’s innovative approach to battery architecture and thermal protection set a benchmark for electric aviation, demonstrating the potential for lightweight, efficient designs. Building on this foundation, the FAA’s eIPP program seeks to accelerate the integration of such cutting-edge technologies into urban air mobility and other advanced applications.

Industry leaders join FAA’s groundbreaking pilot program

In March 2026, U.S. Transportation Secretary Sean Duffy and the FAA announced eight projects selected under the Advanced Air Mobility and eVTOL Integration Pilot Program (eIPP). Spanning 26 states, these projects focus on urban air taxi services, regional passenger transport, cargo logistics, emergency medical response, and autonomous operations. Key industry players participating in the program include Joby Aviation, Wisk Aero, Archer Aviation, and Beta Technologies. Joby is targeting the launch of passenger services in Dubai later this year. Flights under the eIPP are set to begin this summer, with cargo operations expected to lead due to simpler liability concerns, less congested airspace, and the fact that paying passenger services in U.S. urban airspace remain at least a year away.

Why automotive solutions don’t work in the air

In the very early days of electric aircraft development, the default assumption was to apply the same thermal runaway management approaches used in electric vehicles (EVs). It quickly became clear that this was the wrong starting point.

The distinction comes down to consequences. When an EV battery goes into thermal runaway, you pull over, get out, and call 911. When an aircraft battery does the same, there is nowhere to go. Automotive thermal protection standards are essentially egress standards, where the goal is to buy the occupants enough time to escape. Heavy steel enclosures, thick ceramic shields, and dense insulation are all acceptable solutions when you’re already moving a two-ton vehicle down a road.

In aviation, every gram of thermal protection material is a gram taken from battery energy, range, or payload. An electric aircraft engineered to automotive containment standards may simply be too heavy to fly commercially, or even at all. Beyond weight, the problem is structurally different: an aircraft battery must keep the vehicle airborne during a thermal event, not merely slow a fire long enough to open a door. It must do so at altitude, under vibration, and with reduced atmospheric pressure, which changes how gases vent and how fires propagate.

The result is a completely different design problem, requiring thin, light, thermally capable materials rather than the brute-force containment hardware that works perfectly well in a parking lot.

An unexpected gift to conventional aviation

Here is where the story takes an ironic turn. The brutal material requirements imposed by electric aircraft — where there is simply no room for heavy conventional solutions — have forced a new generation of ultra-light, high-performance thermal protection systems and flame barriers into existence. These are material combinations that either didn’t exist commercially before or hadn’t been considered for aerospace applications.

And now those innovations are flowing back upstream. Traditional aerospace manufacturers, who have relied on combustion engines and legacy materials for decades, are finding that the thermal protection systems and flame barriers developed under pressure for electric aviation outperform what they had been using all along, and at a fraction of the weight.

Managing transient thermal events — whether from flames, fires, battery failures, or aerodynamic heating — will always be fundamental to aircraft battery design. The pioneers building tomorrow’s electric aircraft batteries are inadvertently solving yesterday’s problems, giving the entire aerospace industry access to materials that are thinner, lighter, faster to install, and more thermally capable than anything that emerged from the conventional development program.