For the first time, a hybrid-electric plane has taken to the skies above Maui.

Ampaire Inc., a Los Angeles-based company focused on electric aviation, conducted its first, 20-minute demonstration flight in its Electric EEL — a hybrid-electric plane – from Maui’s Kahului Airport to Hana and back on Nov. 22 on a single charge.

Ampaire said it is the first to complete a demonstration flight of a hybrid-electric aircraft along an actual airline route. Ampaire is now flying the route regularly as part of a one-month demonstration program in partnership with Mokulele Airlines. Mokulele is one of 15 airlines around the world that signed a letter of interest with the company.

“We’re following the successful path of hybrid-electric automobiles in transforming ground transportation by taking that model to the sky, ” said Ampaire CEO Kevin Noertker in a news release. “By upgrading current aircraft with hybrid-electric propulsion we can enter the market quickly and take advantage of existing infrastructure for fixed-wing aviation.”

It is also the first use of a hybrid-electric aircraft under the Federal Aviation Administration’s Experimental-Market Survey category, according to Ampaire, which allows the company to fly with its crew and essential personnel for training and exploratory market purposes.

The Electric EEL is a retrofit of the popular, six-seat Cessna 337 twin-engine piston plane. In the rear, the plane still has a 300-horsepower piston engine, and in the front, a 160-kilowatt, electric power unit, plus a battery pack carried in an under-fuselage shell.

It’s a parallel hybrid plane, Noertker said, similar to a “Prius flying in the skies,” and the first of its kind in the world.

On the ground, a Mokulele hanger was wired with a 208-volt, 3-phase outlet. Ampaire said it is working with the Hawaii Department of Transportation and Hawaiian Electric to explore longer-term infrastructure solutions for a fleet of hybrid- or fully-electric aircraft.

The electric power unit reduces fuel consumption and carbon dioxide emissions from the hybrid plane by about 40 to 50%, according to Ampaire.

“Fuel cost is the largest cost item for airlines,” said Noertker in a video, “so hybrid electric planes will lower the cost of air travel across the board and enable these airlines to fly routes more frequently and a greater diversity of routes as well, increasing service to communities that currently don’t have adequate air service.”

Noertker said Ampaire is about three years from having an aircraft certified by the FAA to carry passengers commercially.

Ampaire’s long-term goal is to make the hybrid planes commercially available for short-haul flights in markets like Hawaii in order to reduce greenhouse gas emissions.

“We can take lessons from this series of flights and apply them to subsequent, larger aircraft designs already in the works,” said Noertker.

Ampaire is exploring larger aircraft conversions with support from NASA and the U.S. Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) research arm.

“The market for electric aircraft will expand as airlines perceive that electric aviation is not only environmentally desirable, but economically advantageous,” he said. “Electricity cost is an order of magnitude less expensive in comparison to fuel, which is the largest cost item for airlines.”

In June, Ampaire marked a milestone with its first test flight of a hybrid-electric plane in southern California. The first demonstration flight on Maui was originally anticipated to take place in the fall of last year, but was delayed for numerous reasons, including the COVID-19 pandemic.

“The future for regional airlines is electric,” said Stan Little, CEO of Southern Airways, which owns Mokulele Airlines, in the release. “We expect to put hybrid- and all-electric designs into service as soon as possible, and we know other regionals are watching us with great interest.”

The flight trials are supported by Elemental Excelerator, a global climate-tech accelerator which selected Ampaire as part of its portfolio in 2018.