United Airlines backs supersonic startup Astro Mechanica in latest bet on future flight
August 20, 2025
United Airlines’ venture capital arm, United Airlines Ventures (UAV), has quietly taken a strategic stake in Astro Mechanica, an aerospace startup pioneering advanced airframe and propulsion technologies for supersonic aircraft
While the exact investment remains undisclosed, Axios reports that the startup raised around $27 million earlier this year from investors including Andreessen Horowitz, Lowercarbon Capital, and Giant Step.
UAV partner Mukul Hariharan said Astro’s Duality™ propulsion concept – a hybrid-electric system that can switch from turbofan to turbojet to ramjet modes – caught their eye for its operational flexibility and maturity path combining early defence applications with later commercial use.
I've kept a pretty low (online) profile of what I'm building, but word's getting out.
— Ian Brooke (@k2pilot) February 29, 2024
My company Astro Mechanica has invented a new kind of jet engine. Unlike any existing engine, it's efficient at every speed. Because it's efficient at every speed, we can use it in a new way:… pic.twitter.com/YecrslCiPZ
“They’re attacking the engine problem from a novel but somewhat obvious way, given electrification trends,” Hariharan, a former commercial airline pilot, tells Axios. “They look at a problem from a different angle, and they found a different way to attack it, and they have the business flexibility to actually approach it, versus a Pratt & Whitney or Rolls-Royce or whoever else.”
Who is Astro Mechanica, and what are they building?
Astro Mechanica, based in Chicago and backed by Y Combinator, describes itself as reinventing supersonic flight “from the engine forward.” Its flagship engine, Duality™, is claimed to deliver efficiency across all speeds, promising efficient operations from subsonic take‑off to Mach 3+ cruise.
This Turboelectric Adaptive Engine uses electric motors to separately drive the fan and combustor, instead of both being mechanically linked. Powered by a turbogenerator, this system allows the engine to function as either a turbofan or a turbojet with seamless flexibility.
initial test data suggests this feels extremely good for the engine pic.twitter.com/Wgmy1w94fD
— Ian Brooke (@k2pilot) October 19, 2024
This innovation enables optimal performance across all speeds, especially supersonic regimes. It’s a novel approach unmatched by traditional turbofan-only designs.
Uniquely, it’s designed to run on liquefied natural gas (LNG), a fuel that emits 30% less CO₂ and costs around one-tenth the price of jet fuel. While using LNG introduces infrastructure challenges, the engine’s modular energy source means it can also operate on conventional jet fuel if needed.
The company’s roadmap is aggressive. Having built a proof-of-concept engine in just two months, they aim to produce a flight-capable engine in three months using off-the-shelf hardware.
Following this, the company aims to build an airframe within 6‑8 months, leading toward their first supersonic flight demonstration by 2025.
Development phases target both military-grade applications and eventual commercial scalability.
United Airlines hedges its bets on supersonic technology
This investment complements United’s existing bet on Boom Supersonic. In 2021, the airline signed a major order for 15 Boom Overture jets, with options for 35 more, aiming for entry into service around 2029.
Boom’s development is progressing. Its XB‑1 demonstrator broke the sound barrier in early 2025 without producing an audible boom, and its full-scale Overture airliner is slated for first flight in 2027, aiming for rollout by 2029/2030.
Boom approached the supersonic challenge from the opposite direction, designing the aircraft first and dealing with the propulsion later. The company had originally planned to use a third-party engine for the jet, but is now developing its own in-house solution known as Symphony.
United is now diversifying within supersonic development, investing in two distinct technology pathways. This hedge helps spread technological and regulatory risks.
Beyond supersonics, UAV has built a broad innovation portfolio since its 2021 launch, backing over 30 startups across aerospace, tech, and energy‑transition sectors.
Some of its notable investments include blended wing body aircraft manufacturer JetZero, Archer Aviation’s eVTOL, Heart Aerospace’s electric turboprop and various carbon removal and sustainable aviation fuel projects.
