British Airways, Bill Gates, the UK government and an assortment of venture capitalists are among those supporting ZeroAvia's hydrogen propulsion plans.
Otto Aviation, which is developing a six-seat, aero-diesel powered aircraft, announced it will also create a zero-emissions version of the Celera 500L.
World Fuel Services has rolled out an enhanced carbon offset program that makes it easier for flight departments and FBOs to meet their carbon targets.