The Future of Advanced Air Mobility

On July 16, 2019, Karem Aircraft was granted a patent covering technology it intends to use in the development of the Butterfly eVTOL aircraft. The design will be based on the patented Optimum Speed Rotor technology previously developed by company founder Abe Karem.

Also on July 16, 2019, Karem announced that it has raised $25 million through a Series A funding round. The main backer for this was South Korean industrial group Hanwha Systems. The funding was approved on December 8, 2019, by the U.S. Committee on Foreign Investment in the United States. It will be used to launch a new spin-off company called Overair (earlier referred to as K4 Aeronautics) that will bring the Butterfly to market and establish an air-taxi operation in support of Karem’s partnership with Uber Air. In the future, Karem Aircraft will mainly focus on its activities in the defense market.


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

The strong track record in advanced unmanned aircraft development of Karem Aircraft founder Abe Karem provides foundational credibility for the company's plans in the eVTOL market. The 82-year-old engineer was instrumental in creating prominent military drones such as the General Atomics Predator.

More currently, the $25 million raised in a Series A funding round completed in July 2019 provides fresh resources for the program, which now has the support of South Korean industrial group Hanwha Systems. The official approval of this new venture was a significant breakthrough. However, the investors have yet to publish a timeline for the program. 

Since Karem has provided almost no specific details about the Butterfly's projected performance, it is hard to judge how strong a contender it will prove to be.

Butterfly Models

Butterfly Specifications

Optionally-piloted vtol Lift + Cruise


  • Passenger Capacity
  • Range
  • Cruise Speed
    200 mph
  • Powerplant Type
    multi rotor
  • Power Source
  • Endurance
  • Max Altitude
  • Takeoff Distance
  • Landing Distance
  • Empty Weight
  • Payload Weight


  • Length
  • Width
    45 ft
  • Height
  • Wingspan

As of July 2019, Karem Aircraft had provided almost no details about its design for the Butterfly air taxi. The Butterfly design uses Karem’s patented Optimum Speed Rotor technology to drive a vectored thrust powerplant with four large tilting rotors mounted on the wings and tail. According to the company, this will overcome the acknowledged eVTOL tradeoff between hover and cruise flight efficiency. Without providing any projected specifications or performance figures, it claims that the large, slow-turning rotors will provide both efficient lift and low noise levels needed to meet requirements for operating in urban areas.