By Bjorn Fehrm

June 25, 2025, © Leeham News at Paris Air Show: The low or no emission propulsion discussion started at the 2014 Farnborough Air Show when Airbus’ E-Fan prototype flew in front of a surprised crowd. Everyone then thought that low-emission electric propulsion aircraft would be common before 2020.

It took 11 years and as many air shows before a certifiable battery-electric aircraft would fly again at an air show, this time at the 2025 Paris Air Show (Figure 1). Of the over 100 announced projects to develop and produce a battery electric passenger aircraft, it was the Alia CX300 from BETA Technologies that succeeded.

The story of BETA Technologies’ Alia CX300 is, in many ways, the story of the Ugly Duckling that grew to become a White Swan.

Figure 1. The BETA Alia CX300 battery-electric cargo version ready for its daily Paris Air Show flight. Source: Paris Air Show.

The story of the Alia CX300

The Alia CX300 is the offspring product from BETA Technologies’ development of an Alia 250 eVTOL. BETA Technologies is an electric aircraft developer based in Burlington, Vermont. It was founded in 2017 by its CEO, Kyle Clark.

The  CX300 was never to be, as it’s an afterthought of the original focus product of BETA, the eVTOL Alia 250.

Clark, who is the CEO but also an engineer and the company’s first test pilot, set out to develop an eVTOL cargo aircraft for BETA’s main investor Martine Rothblatt, who had made a fortune from starting up Sirius Satellite Radio and then founded United Therapeutics, a biotech company based in Silver City, Md. Rothenblatt sought an air vehicle that could fly organs for transplantation between hospitals. A low-noise eVTOL would be ideal for such transports.

To develop the vertical takeoff and then conventional forward flight Alia 250, Clark’s team started by flying the Alia 250 without lift motors, using the pusher motor for Conventional Take Off and Landing (called CTOL flight), Figure 2.

Figure 2. The Alia 250 in the initial configuration without lift motors and rotors. Source: BETA Technologies.

As part of the in-house electric motor and battery system development, BETA flew the Alia 250 prototype in conventional flights at long distances, first in the vicinity of its development site in Burlington, Vermont, but then on gradually longer flights from its test center in Plattsburgh, NY.

The tricky transition of an eVTOL

The strategy to first develop the CTOL part of Alia 250 turned out to be BETA’s ingenious stroke. The most dangerous and tricky part of making an eVTOL is not the hovering part. It’s reasonably straightforward and even easier to master than the complicated hovering of a single rotor helicopter. By having more rotors than one, you can vary the RPM of the rotors and thus achieve stability in the same way as a drone.

As all eVTOLs employ Fly-By-Wire control of the rotor RPMs, a lot of the stability manipulations of the eVTOL when hovering can be made without nagging the pilot for corrections.

The tricky and dangerous part is the transition from hovering into forward flight. As you start the movement forward, your wings are close to the circular wash field of the rotors (reminiscent of the dangerous ring wash flow of the V22 Osprey, but now four or more rings instead of the Osprey’s two rings). At the same time, the wing and empennage’s horizontal and vertical tails are stalled due to the low forward speed.

The transition from the empennage and wing passing from a stalled condition (where they deliver drag but no lift) to a non-stalled condition, when they start to add lift to the hover lift, is very tricky. The rotors must instantaneously compensate for all lift force shifts without causing such disturbances of the overall flow field that the wing or empennage runs into oscillating stall to no-stall.

This is the phase of flight where the aeronautical world has little to no previous experience, and which takes a lot of time to carefully and gradually explore. Once mastered at no or low wind conditions, it must be handled at strong sidewinds and then in all the possible failure cases when one rotor goes inoperative, etc.

From Ugly Duckling Alia 250 prototype to CX300 Swan

While every other battery electric eVTOL project encountered delays and problems during the exploration of these flight phases, BETA opted to fly conventionally first and then tackle the vertical and transition phases. And it flew in CTOL mode very successfully. The eVTOL competition wasn’t overly concerned, as BETA hadn’t yet cracked the vertical and transition phases, and they knew it would be time-consuming.

But the many CTOL battery-electric projects started to take notice. How could BETA fly long distances in conventional mode with seemingly no problems? The background was that Clark started his engineering career as an electric design engineer, building demanding power supplies for magnesium metal molding through induction.

So, Clark and team knew how to make power supplies for batteries and learned to make electric motors. Then, Clark added aeronautical knowledge when training to be a test pilot. BETA is about down-to-earth, gradual development by a dedicated and knowable team, led by a “do it yourself but well” Kyle Clark.

At a point, the operators waiting for the battery electric projects had had enough.  With no certification-conforming prototypes from projects like eViation Alice, Volt Aero Cassio, Heart Aerospace ES, or Aura Aero, the cleaned-up Alia 250, now named Alia CX300, became the way to start exploring electric flight operations. Operators told BETA to convert the Alia 250 into a CTOL CX300, so that it could be produced and ordered.

The Ugly Duckling, the Alia250 prototype with missing lift engines and propellers, thus became the first battery electric cargo and passenger aircraft in serial production. The CX300 has an operationally relevant range on battery power and can accommodate either 200 square feet of cargo or five passengers. Including IFR reserves, it can fly 200nm legs. And it will be certified for VFR and IFR flight this year according to BETA.

Figure 3. BETA Alia CX300 getting ready for a Paris Air Show flight. Source: Leeham Co.

Given the straightforward design, the years of successful flight of the prototypes, a decent range, and its current production status, early adopters are now ordering it to begin their operational experience with battery-based aircraft. Early adopters, such as the UK Bristow group, a large helicopter operator that has ordered the CX300 to fly on some of its Norwegian routes, and Air New Zealand, which has ordered up to 23 Alia CX300 for cargo operations, are operators that have waited long for other projects.

Now, others will get off the fence and use the CX300 to gain first operational experience of battery-electric cargo and passenger transport.

CX300 development and the path to eVTOL

The CX300 is a FAR Part 23 six-seater where the pilot takes one seat. It can carry five passengers or 1,500 pounds of cargo. As a five-passenger aircraft, it leaves four seats on the table compared to the ubiquitous Cessna Caravan nine-seater. Could the CX300 be stretched to carry four more passengers? I think so. Should the demand be there, I think we will see a nine-passenger-seat variant of the CX300.

Operators that start with the Alia CX300 will have an easy upgrade to the eVTOL Alia 250. The aircraft is vertically identical, with four 450kW quad redundant lift motors and rotors added. It will tax the battery system, which for the CX300 consists of five 45kWh modules, providing a total capacity of 225kWh, driving the 300kW cruise motor. But BETA says 200nm should be possible with helicopter reserves for the eVTOL Alia 250.

If the BETA CX300, along with its charging infrastructure (also manufactured by BETA), functions well, there is every reason to continue with BETA when transitioning to eVTOL. And should BETA stretch the CX300 to a nine-seater, it will be a viable alternative to a Cessna Caravan for short sectors.