FARNBOROUGH, England: GE Aerospace on July 20 announced what it said was the world's first high-altitude flight assisted by hybrid-electric propulsion, marking a milestone in its efforts to develop technologies for the next generation of commercial aircraft engines.

The flight, conducted at an altitude of more than 30,000 feet, used a Saab 340 aircraft that has been carrying out similar trials since May. The aircraft also completed a transatlantic journey with stopovers before making its debut at this year's Farnborough International Airshow.

The research is being carried out in partnership with NASA and electric aerospace company BETA Technologies as engine makers develop technologies for potential successors to the Boeing 737 and Airbus A320neo.Supporters of hybrid-electric propulsion say combining conventional and electric power can help aircraft climb more efficiently while contributing to lower fuel consumption and emissions."It leads to the next step in aviation propulsion," BETA Chief Executive Officer Kyle Clark told a news conference.

Hybridization is one of four key research areas under the RISE engine program being developed by CFM, the engine maker jointly owned by GE Aerospace and France's Safran.

The RISE program also includes an open-fan engine design, while the company is also developing a conventional enclosed alternative known as AD-L, or ADNB, Reuters has previously reported.

After years of showcasing concepts through artist's impressions and computer-generated images, engine manufacturers are increasingly demonstrating real-world progress toward the fuel efficiency and durability targets required for the next generation of aircraft engines expected later in the next decade.

"Simulation has given way to real world innovation," GE Aerospace Commercial Engines CEO Mohamed Ali said.

GE's competitors, Pratt & Whitney and Rolls-Royce, are expected to provide updates on their own engine research later this week.

Ali declined to provide details on how the high-voltage hybrid-electric system, which replaces one of the conventional engines on the Saab 340 test aircraft, would be incorporated into a future commercial engine. "This certainly would become a significant enabling technology," he said.

Industry sources say Boeing, which has shown less willingness than Airbus to adopt open-fan engine designs, has expressed concerns about the added weight of hybrid systems, including the three additional cooling inlets visible on the engine displayed at the airshow.

Ali said balancing weight and performance is part of the normal process of designing engines for commercial use.