United Airlines took a sizable step toward a sustainable-fuel future for aviation Wednesday with a flight from Chicago to Washington, DC with one engine running on conventional fuel and the other on a sustainable fuel made from non-petroleum sources. The flight, on a 737 Max 8, carried over 100 passengers.
The use of two separate fuels kept the flight under FAA rules that allow only up to 50% sustainable aviation fuel (SAF), while at the same time allowing the two engines and their operation to be compared directly.
United, Boeing, engine supplier CFM and the fuel supplier, a subsidiary of Marathon Oil hope the flight will help lead to approval for more use of SAF. The fuel used is described as a ‘drop-in’ fuel that can be substituted for the usual petroleum-based fuel without modifying the aircraft fleet.
