Hybrid airships are between airplane and airship, they have wings that provide lift, but they are still airships. What about large airplane like Airbus Beluga or Boeing Dreamlifter, filled with helium. Large compartment that is normally used for cargo filled with helium, and below that passenger compartment. So they would be very large size passenger planes (or cargo planes) with very large amount of internal volume filled with helium and then passenger or cargo compartment that is much smaller in volume. They would have lower speed and lower flying height than nowdays passenger planes, but they would be economical because helium offers lift. Also takeoff will be shorter and they get faster up the runway and don t waste fuel in takeoff and rising to flying altitude because of helium lift, and they will fly lower anyway. Autogyro is another aircraft. Their rotor is not powered, it simply uses airflow to provide lift. What about large autogyros, size like Mil Mi 12 Or Mi 26, one rotor over hull or two rotors over wings like in those two helicopters. Those aircrafts would be airplanes with autogyro rotors, not helicopters. Rotors offer airlift but don t need power so those extra large autogyros would be economical. Hybrid airplane with helium compartment and autogyro can be combined, they have both large helium tank in the hull and also one or two large autogyro - rotors. In the hull can be two rotors like in big helicopters and in wings two more, so large airplane can have four autogyro rotors. Because hybrid airships are just airships with some airplane -like qualities, airplane with some airship- like qualities (helium storage) can be called hybrid airplane then. Airships can use ducking flying method / zig-zag flight, airship rises and then dives and glides with low power. Helium filled airplanes / autogyros can use same thing, but also use their engines during dive, using lower power in diving phase than during flying straight or rising. If instead of jet engines they use electric motors and propellers in engines and accumulator to provide power, or hybrid method gasoline or diesel engine with accumulator and electric motors. Accumulator is used when low power is needed and combustion engine with generator (in airplane hull) that makes electricity for electric motors when high power is needed. If airplane motors are electric, in diving phase electric motors and propellers could be used in reverse, using them as generators that provide electric energy to accumulator, using energy of airflow in diving phase for propeller-charging the batteries / accumulator. Using helium lift and autogyro rotors airplane can use ducking flight method to save energy, and if flying motors are electric, airplane can use airflow to charge batteries in diving phase so energy usage is even less. So hybrid airplane rises and then dives during flight. But helium or autogyro method can be used in normal type airplanes also that have very wide-bodied hull for helium storage or autogyro rotors or both, without ducking flight method. Turbodiesel engines can be used, instead of two or four large jet or turboprop engines, many turbodiesel engines can be in wings from root to tip, using biodiesel fuel instead of jet kerosine. Two diesel engines can be coupled in H-engine (or X-engine) configuration to drive common propeller, if H- or X- engine arrangement is mechanically suitable for aircraft engines. Four engines can be connected to form 4 motor H-engine or X-engine, if it is mechanically possible, to drive one propeller. Some merchant and warships use four engines connected to one propeller shaft, but how this arrangement works in airplane engines I don t know. Diesel or electric engine propelled aircraft would be like Super Guppy, filled with helium and with or without autogyro rotors. Jet powered large aircraft would be like Airbus Beluga, without autogyro rotors but with large hull filled with helium. Diesel engines that use Wankel- type rotating cylinder etc. new efficient combustion engine types can be used in airplane engines, altough most of new combustion engine types are in experimental stage. But some new combustion engine types that are more fuel efficient / more power to weight ratio efficient than nowdays diesel or gasoline engines, are more or less production ready. Helium offers lift so internal structure of those large airplanes can be made lighter, because if hull is filled with helium it is self-supporting structure and can be build to be much lighter than Super Guppy or Airbus Beluga. So helium offers both lift and also makes airplane structures lighter at the same time.