That’s why we have to be very smart about how and how much we are hybridizing the propulsion system.

Using batteries as a power assist during takeoff and climb are very promising options. Taxiing to the runway using just electric power could also save a significant amount of fuel and reduce the local emissions at airports. There is a sweet spot between the added weight of the battery and how much electricity you can use to get net fuel benefits. This optimization problem is at the center of my research.

Hybrids would still burn fuel during flight, but it could be considerably less than just relying entirely on jet fuel.

I see hybridization as a mid-term option for larger jets, but a near-term solution for regional aircraft.

For 2030 to 2035, we’re focused on hybrid turboprops, typically regional aircraft with 50-80 passengers or used for freight. These hybrids could cut fuel use by about 10%.

With electric hybrids, airlines could also make more use of regional airports, reducing congestion and time larger planes spend idling on the runway.

Shorter term we’ll see more use of sustainable aviation fuels, or SAF. With today’s engines, you can dump sustainable aviation fuel into the same fuel tank and burn it. Fuels made from corn, oilseeds, algae and other fats are already being used.

Sustainable aviation fuels can reduce an aircraft’s net carbon dioxide emissions by around 80%, but supply is limited, and using more biomass for fuel could compete with food production and lead to deforestation.

A second option is using synthetic sustainable aviation fuels, which involves capturing carbon from the air or other industrial processes and synthesizing it with hydrogen. But that’s a complex and costly process and does not have a high production scale yet.

Airlines can also optimize their operations in the short term, such as route planning to avoid flying nearly empty planes. That can also reduce emissions.

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