The Lilium Jet, the Thirty-Six Electric Fans Inside the Wing, and the Engineering Bet That Survived a Bankruptcy to Try Again

The Lilium Jet is a seven-passenger electric aircraft with 36 ducted fans buried inside its wings, capable of vertical takeoff and 300-kilometer cruise - a design that prioritizes regional range over the short urban hops most eVTOL competitors target. The company behind it filed for insolvency in October 2024, but American investors acquired its assets and reformed as a new Munich-based entity in early 2025. What survived the bankruptcy may matter more than what failed.

What Makes the Lilium Jet Different From Every Other eVTOL

From the outside, the aircraft looks like a small business jet with no visible propulsion. No rotors, no propeller discs, no exposed spinning machinery. What you can’t see are the 36 electric ducted fans embedded along the canard and main wing - each mounted in an assembly that rotates 90 degrees. Pointed down for hover and transition, pointed aft for cruise.

The flight control system manages all 36 simultaneously, making thousands of adjustments per second to hold the aircraft stable as it moves between vertical and horizontal flight modes.

The Engineering Argument for Putting Fans Inside the Wing

Most eVTOL aircraft use open propellers - visible from outside, exposed to the airstream during cruise. At the low speeds urban air taxis fly, that drag is manageable. At higher speeds, it consumes a significant portion of the energy budget. Open rotors designed around hover also run at off-optimal conditions in fast forward flight, adding an efficiency penalty.

The Lilium team chose a different path: embed the propulsion inside the wing. A ducted fan enclosed in a short nacelle shapes incoming and outgoing airflow in ways that can improve efficiency in certain speed regimes. More importantly, in cruise, the fans push air through ducts that are part of the aerodynamic surface itself. The external drag profile looks like a conventional fixed-wing aircraft.

That efficiency difference in cruise is the range difference. The range difference is the market distinction.

The Hover Penalty and Why It Doesn’t Kill the Concept

The cruise advantage comes with a real cost in hover. The relevant physics involve disk loading - thrust produced per unit of fan or rotor disk area.

Large, slow-turning rotors move a high volume of air at low velocity and produce lift efficiently. The kinetic energy wasted per unit of thrust scales with the square of exit velocity: accelerate less air faster and hover becomes more expensive. Small, fast-spinning ducted fans have high disk loading. In hover, they are less efficient than large open rotors doing the same job.

For the Lilium mission, hover is a small fraction of total flight time. Five minutes of hover and transition at each end of a 40-minute cruise represents roughly 20 percent of the total mission. If the cruise efficiency gain is large enough - and Lilium’s engineers believed it was - the net energy for the full trip is lower than a multirotor flying the same route.

Whether that math holds with real-world batteries is the question the program was built to answer.

Why Regional, Not Urban

The majority of the eVTOL industry has targeted urban air mobility: short hops within a metro area, typically 60 to 100 miles. Those aircraft skip traffic, not geography.

Lilium aimed at a different problem. Its 300-kilometer (~185-mile) range at a cruise speed of ~250 kph (~155 mph) targets the gap between cities too far to drive conveniently but without viable direct airline service - the 90- to 200-mile city pairs that regional turboprops once served before airline consolidation made those routes uneconomical. That is a much larger addressable market than urban air taxi services, but it demands range the urban vehicles weren’t designed to deliver.

The Battery Problem Hasn’t Been Solved

Lithium-ion production cells today store approximately 250–300 watt-hours per kilogram of usable energy. Jet-A fuel stores roughly 12,000 watt-hours per kilogram - a ~40-to-1 gap. Every kilogram of battery buys 40 times less energy than a kilogram of fuel, and unlike fuel, battery mass doesn’t decrease as the aircraft burns through its energy reserve.

Lilium’s published range targets required battery performance above what production cells delivered when those targets were written. The engineering team was projecting forward on an improvement curve that has historically delivered 5–8 percent more energy density per year. The question was whether the certification timeline and the battery curve would intersect at the right moment.

They didn’t - at least not in time for the first company.

From SPAC to Insolvency: The Capital Story

In 2015, Daniel Wiegand and three colleagues from the Technical University of Munich founded Lilium as an outgrowth of a graduate project on jet-powered VTOL aircraft. Early test flights with a two-seat remote-piloted demonstrator proved the concept: vertical takeoff, transition to horizontal flight, landing. The control system held it together.

By 2022, a prototype significantly closer to the final production configuration was flying.

In 2021, Lilium went public through a SPAC merger with Qell Acquisition Corp, raising roughly $600 million in capitalization and listing on Nasdaq. The combined entity was valued at over $3 billion. The logic held: capital markets would fund the development gap while investors accepted a five-to-seven-year path to type certification.

By 2023, rising interest rates had compressed eVTOL valuations broadly. Certification timelines had slipped industry-wide. Revenue remained years away. Follow-on funding rounds Lilium needed did not close. An attempt to secure bridge financing from the German government did not succeed.

In October 2024, Lilium GmbH filed for insolvency.

What the New Owners Actually Acquired

A group of primarily American investors purchased the assets out of the insolvency proceeding. New Lilium GmbH was established in early 2025, Munich-based, with a stated commitment to continuing the EASA type certification program.

What those investors acquired was not just IP and hardware. In 2020, EASA - the European Union Aviation Safety Agency - issued a type certification basis for the Lilium Jet. That document defines the airworthiness standards the aircraft must meet to receive a type certificate. For a tilting distributed-fan aircraft with no conventional flight control surfaces in the traditional sense, writing that document required EASA to develop entirely new standards. That work took years.

A type certification basis is not a type certificate. But it represents EASA’s formal institutional engagement with this specific design. That knowledge is not transferable to a different aircraft - it belongs to the Lilium Jet and the engineers who built it.

The FAA has bilateral airworthiness agreements with EASA. Certification data and safety analysis developed under EASA standards are directly relevant to any subsequent FAA review. The path to the American market runs through the work already done.

What the Joby Comparison Tells You

The eVTOL companies that survived the first round of market compression were the ones with capitalization deep enough to outlast longer-than-projected certification timelines. Joby Aviation is the clearest example: well-capitalized, methodical, and the recipient of the first FAA eVTOL type certificate in 2024 - a process that took close to a decade.

The Lilium design is harder to certify than a conventional multirotor air taxi. Novel airworthiness standards require more regulatory work, which requires more time, which requires more capital. The first attempt did not survive long enough.

The second attempt inherits the first attempt’s accumulated certification work - and inherits the challenge of executing against a longer timeline than the original company ever projected.

Why This Matters for Pilots

For pilots watching the eVTOL space, the signal to track is battery energy density. The regulatory pathway for novel electric aircraft is now far better understood than it was in 2020. EASA and the FAA have learned from Joby, Archer, Lilium, and others. The certification framework is clearer.

What determines whether designs like the Lilium Jet reach revenue service is whether battery technology - solid-state cells, lithium-sulfur chemistry, or whatever gets there first - improves fast enough before the companies running certification programs run out of capital. That is a materials science question, not an aviation question.

The Lilium Jet flew. The engineering concept is real. The certification work is real. Whether the second company has the runway to finish what the first company started is genuinely unknown.

Key Takeaways

The Lilium Jet uses 36 tilting ducted fans embedded in its wings - a design that trades hover efficiency for superior cruise efficiency, enabling 300 km / ~185 mile range at ~155 mph.
Most eVTOL competitors target urban hops of 60–100 miles; Lilium targets regional city pairs in the 90–200 mile range, a fundamentally different and larger market.
Batteries store ~40 times less energy per kilogram than jet fuel - the core constraint every electric aviation program is racing against.
Lilium GmbH filed for insolvency in October 2024; American investors reformed the company in early 2025 with the EASA certification basis and test flight data intact.
Joby Aviation received the first FAA eVTOL type certificate in 2024 after nearly a decade - the benchmark for what a successful certification timeline in this category actually looks like.