Are there trying to plan on building hybrid-fuel airplanes?

Question

Are there trying to plan on building hybrid-fuel airplanes?

Answer 1

Experimental flights have been made using biofuels.  Biojet fuel will become widely available, and it will solve availability problems for a while, but it will be expensive.

Hybrid technology as in hybrid automobiles is not suited for use in airplanes.  The components are too heavy.

The "easyjet ecojet" is a theoretical proposed standard for a low-noise, low-emissions airliner, and includes some interesting concepts.  The proposal has been around in some format for about 25 years.  It does not include hybrid technology.

Answer 2

Google 'easyjet ecojet'. thats a hybird plane.