Backed by Boeing HorizonX and JetBlue Technology Ventures, the company worked from 2013 to 2018 on a proposed family of hybrid electric regional aircraft of up to 50 seats.

[2] Around the beginning of 2017 they launched plans to fly a prototype hybrid-electric airliner in 2019 or 2020, under the revamped FAR Part 23 rules for electric aircraft standards expected by 2018 and with first type certification by 2020.

[4] Beyond February 2018 Zunum needed $50 million in Series B funding and received bridging loans from JetBlue and Boeing in April, allowing hiring in the summer of 2018.

[3] Zunum has since released information saying that their hardware and technical assets are in their possession and in storage, and that they are currently fundraising for the next chapter of their company.

[6] In November 2020, Zunum Aero filed a lawsuit against Boeing alleging that Boeing tried “to gain access to proprietary information, intellectual property” and then used its dominance “to delay and then foreclose” Zunum's operation, “in order to maintain its dominant position in commercial aviation by stifling competition”, using this proprietary information “to provide a hybrid-electric propulsion system for a different aircraft design” with Safran.

[11] Purchase cost was expected to stay below the list price of a $4.5 million single-engine turboprop such as the Pilatus PC-12 or Cessna Denali.

The evolving batteries would have been certified every two years and introduced often, in line with their anticipated short cycle lives at high utilization rates.