The Future of Advanced Air Mobility

The origin of the eFlyer program was in 2010 when privately owned Bye Aerospace started developing a proof-of-concept for an electrically powered version of the ubiquitous Cessna 172 light aircraft. This plan was subsequently abandoned and, in February 2014, Bye started working on plans for its own two- and four-seat electrically powered fixed-wing aircraft. The program started life under the name Sun Flyer before it was rebranded as eFlyer in April 2019. In April 2018, the U.S. Federal Aviation Administration accepted Bye's application to seek certification of the aircraft under FAR Part 23 rules. 

The two-seat eFlyer 2 and four-seat eFlyer 4 are being developed for a variety of general aviation applications, including flight training and passenger charter flights. As of December 2018, Bye had collected 220 deposits, split evenly between the two models. The deposit for the eFlyer 2 (priced at $394,000) is $5,000, rising to $10,000 for the larger eFlyer 4 (priced at $449,000). The company claims that the target market for the eFlyer is around 20,000 aircraft over the next 20 years (with a combined value of $7.2 billion). In November 2019, it indicated that intends to announce further versions of the eFlyer family. 

On February 2, 2019, an eFlyer 2 prototype made its first flight powered by the Siemens SP70D motor selected as the eFlyer powerplant. It provides a peak power rating of 120 HP and a continuous rating of 94 HP. A prototype powered by a different motor had made its first flight on April 10, 2018. As of July 2019, the company said it was close to completing the critical design review. It expects to achieve FAR Part 23 type certification for the eFlyer 2 in 2021. The eFlyer 4 is expected to make its first flight in late 2020 or early 2021, and to complete certification within a "year or so" of the eFlyer 2.

In May 2019, Bye Aerospace received two major orders for the program. General aviation marketplace BlackBird signed a contract to buy the first 100 eFlyer 2s and eFlyer 4s. The San Francisco-based group intends to be ready to start flight demonstrations in 2020. Flight training group OSM Aviation agreed to buy 60 eFlyer 2s, with first deliveries expected in late 2021. As of July 2019, it was reporting commitments for over 600 aircraft, consisting of a mix of the two models.

According to the manufacturer's founder George Bye, it opted to build its program around a conventional fixed-wing airframe based on its conviction that this will deliver better overall energy efficiency. At 20.6, the eFlyer's lift-to-drag ratio is twice as efficient as that of the Cessna 172 at 10. Bye argues that the combination of an electric powerplant and an efficient fixed-wing airfoil can outperform most of the eVTOL concepts depending on rotors. Avionics for both aircraft are from Garmin, which is supplying its G3X touchscreen suite.

In July 2019, Bye Aerospace announced a partnership with UK-based Oxis Energy to develop lithium-sulfur batteries for possible use on the eFlyer. According to Oxis, its Li-S batteries will achieve a power-to-weight ratio of 500 Wh/kg by early 2020 and will deliver a two-fold weight reduction compared to existing lithium-ion batteries. A 12-month development program began in November 2019.

On August 21, 2019, Los Angeles-based air taxi operator Quantum Air announced that it will buy 22 eFlyer 4s and four eFlyer2s. The agreement also calls for the operator to acquire "two future advanced aircraft under development from Bye Aerospace."

By early June 2020, Bye Aerospace had completed the critical design review, which clears the way to the aircraft being built, demonstrated, and tested. The review is also required to comply with FAA's 14 CFR 23 type certification requirements. 

On July 13, 2020, Bye Aerospace announced that it had raised an additional $10 million from two undisclosed venture capital groups. The company said the money will be used to build the first production-conforming example of its eFlyer 2 two-seat model. 

On July 24, 2020, the total number of deposit-backed "reservations" for eFlyer 2 and 4 aircraft had reached 360, with the signing of an order for 10 from UK-based Skyborne Airline Academy. Other customers holding commitments for the aircraft include OSM Aviation and Quantum, Flex Air, Skyborne, Eco Flight, Elfly AS, Blackbird, Aspen Flying Club, Touring Club de France, and Spartan College of Aeronautics.

This level of commercial support almost doubled in early November with the news that South Korean startup Aerospace9 has agreed to acquire 300 aircraft as part of a wider strategic investment in Bye Aerospace. The announcement also included the first official mention of a new nine-seater aircraft called the Envoy, which will have two electric motors, and which Bye said would be formally unveiled "soon." 

Taking account of some disruption caused by the Covid-19 pandemic, Bye Aerospace said in early November 2020 that it now expects the eFlyer 2 to complete FAA Part 23 type certification by the end of 2022, with the larger eFlyer 4 to follow around 12 months later.

On November 16, 2020, Bye announced that its Safran's Electrical & Power division will supply the Engineus 100 electric motors for both the eFlyer 2 and eFlyer 4 aircraft. The French-made motor will replace the Rolls-Royce Siemens motors that have been used during flight testing.

In January 2021, Bye began building series production examples of the two-seater eFlyer 2. The company plans to use the first three production aircraft to complete FAA Part 23 type certification, which they still hope to be completed by the end of 2022. Bye also announced a contract with Oregon-based Composites Universal Group (CUG) for the assembly of the eFlyer 2's fuselage.

In February 2021, Aviation Safety Resources (ASR) successfully completed the first round of tests involving the parachute recovery system intended for use on the eFlyer 2. The test, conducted in Henderson, Nevada, used a load equivalent to the weight of the aircraft and aims to eventually demonstrate a factor of safety of at least 1.15 to prove the system's robustness.

On March 1, 2021, approximately two months after its contract with CUG was announced, Bye reported it had begun work on the fuselage of the serial production example. The company also stated that it is nearing the completion of most of the system-specific certification plans (SSCPs) for the program, and is working on final approval coordination with FAA officials.

In April 2021, Bye confirmed the launch of the Envoy aircraft, rebranding it as the eFlyer 800. This is expected to provide an electric-powered alternative to popular utility turboprops like Textron's King Air family.

As of the end of August 2021, the number of purchase agreements for the eFlyer family exceeded 700 aircraft. Among the customers making commitments during the course of 2021 have been Reykjavic Flight Academy, leasing group Skye, Jet It, and JetClub.

In September 2021, the KLM Flight Academy ordered six eFlyer 2 light aircrafts and eight larger eFlyer 4 aircrafts. In statements from both managing director of the KLM Flight Academy Bard de Vries and Bye Aerospace CEO George Bye the importance of eFlyers creating more environmentally friendly flight academies was expressed. In October 2021, Diamond Aircraft announced an all-electric version of its DA40 trainer which could create competition with the eFlyer in the market of environmentally friendly training aircrafts.

In February 2022, Japanese leasing company Fuyo General Lease announced plans to invest in Bye Aerospace with an unspecified amount. In July 2022, Bye Aerospace announced it was nearing FAA approval for the eFlyer 2.



type certification granted

The eFlyer 4 aircraft will be certified under FAA Part 23 rules.

Missed Projection

type certification granted

The eFlyer 2 will be certified under FAA Part 23 rules.


OXIS Energy and Bye Aerospace have begun a 12-month collaborative program announced in late July that seeks to achieve a 50% to 100% increase in flight time from a single charge on future Bye Aerospace eAircraft.


Bye Aerospace announced it had finalized the supplier agreement with Garmin to to provide the eFlyer 2 aircraft with a full suite of Garmin G3X Touch avionics.  

Bye Aerospace announced that is have received 624 "Customer Commitments" for its series of all-electric eFlyer aircraft.  

This includes: 170 deposits, 318 memoranda of understanding (MOUs), and 136 MOU options.  


Our objective assessment of this program’s probable success.

FutureFlight assesses the probability of success for a new aircraft program by considering the following criteria:

  • Total investment funds available in proportion to the anticipated cost of getting an aircraft certified and in service
  • A company’s in-house capability (in terms of numbers of engineers, technical staff, and customer support teams)
  • The past experience of the company and its senior leadership in developing aircraft
  • The caliber and past experience of key program partners
  • Whether key aircraft systems have been selected and are available for use
  • Whether the preliminary design review has been completed
  • Whether the design for the full-scale prototype has been completed
  • Whether the type certification process has been formally initiated with an appropriate regulator
  • Whether the company has achieved a first flight with a full-scale prototype
  • The number of hours logged in a flight test program
  • Whether type certification has been achieved
  • The number of orders and commitment received for the aircraft
  • Whether the company has adequate facilities to begin series production of the aircraft
Our Methodology

Bye Aerospace has taken a different, and at face value more conventional, approach to many in the eVTOL sector by sticking with a fixed-wing airframe. This significantly reduces the technology and business risks associated with bringing completely new eVTOL designs into service. Its business model is founded on applications like flight training and air taxi operations being early adopters of electric propulsion

The company appears to have solid financial backing and deep reservoirs of aerospace expertise on tap, especially in view of an additional $10 million fund-raising round completed in July 2020. 

Bye's future plans received a further boost from an undisclosed strategic investment by a newly formed South Korean group called Aerospace9. Little more is known about the new partner and its role, but it appears to be related to Bye's plans to announce a new larger member of the eFlyer family, called the Envoy. This nine-seat would mark a significant expansion of its electric aircraft product portfolio, and may indicate some further progress in expanding the performance of available electric batteries.

The company's commercial prospects have been boosted significantly with a flurry of provisional orders for the eFlyer family that exceeded 700 units as of the end of August 2021. These cover a mix of the eFlyer 2, 4, and 800 models.

eFlyer Models

eFlyer 4 Specifications

local stol Fixed Wing


  • Passenger Capacity
  • Range
  • Cruise Speed
    165 mph
  • Powerplant Type
  • Power Source
  • Endurance
    252 min
  • Max Altitude
  • Takeoff Distance
  • Landing Distance
  • Empty Weight
    3,400 lb
  • Payload Weight
    850 lb


  • Length
  • Width
  • Height
  • Wingspan
    38 ft

The four-seat eFlyer 4 is expected to achieve its first flight in either late 2020 or early 2021. Bye Aerospace believes it can complete FAR Part 23 type certification of the smaller eFlyer 2 model in 2021.

It has a 110-kW electric motor (90-kW continuous power rating).

As of November 2019, Bye Aerospace was unable to provide full specifications and performance details for the eFlyer 4 model.


Total Amount Invested: $15m