Aircraft built with two main wings (or three in a triplane) can usually lift up to 20 percent more than can a similarly sized monoplane of similar wingspan, which tends to afford greater maneuverability. The struts and wire bracing of a typical biplane form a box girder that permits a light but very strong wing structure.

On the other hand there are many disadvantages to the configuration. Each wing negatively interferes with the aerodynamics of the other. For a given wing area the biplane produces more drag and less lift than a monoplane, but this effect can be slightly reduced by placing one wing forward of the other though NACA research into this suggests that the reduction of drag is minimal.

A biplane is a fixed-wing aircraft with two main wings. The Wright brothers' Wright Flyer used a biplane design, as did most aircraft in the early years of aviation. While a biplane wing structure has a structural advantage, it produces more drag than a similar monoplane wing. Improved structural techniques and materials and the need for greater speed made the biplane configuration obsolete for most purposes by the late 1930s.

General aviation is a catch-all covering other kinds of private and commercial use, and involving a wide range of aircraft types such as business jets (bizjets), trainers, homebuilt, aerobatic types, racers, gliders, warbirds, firefighters, medical transports, and cargo transports, to name a few. The vast majority of aircraft today are general aviation types.

Within general aviation, there is a further distinction between private aviation (where the pilot is not paid for time or expenses) and commercial aviation (where the pilot is paid by a client or employer). The aircraft used in private aviation are usually light passenger, business, or recreational types, and are usually owned or rented by the pilot.

A military aircraft is any fixed-wing or rotary-wing aircraft that is operated by a legal or insurrectionary armed service of any type. [5] Military aircraft can be either combat or non-combat:

Combat aircraft are aircraft designed to destroy enemy equipment using its own armament.[5]
Non-Combat aircraft are aircraft not designed for combat as their primary function, but may carry weapons for self-defense. Mainly operating in support roles.

The rotor of a helicopter, may, like a propeller, be powered by a variety of methods such as an internal-combustion engine or jet turbine. Tip jets, fed by gases passing along hollow rotor blades from a centrally mounted engine, have been experimented with. Attempts have even been made to mount engines directly on the rotor tips.

Helicopters obtain forward propulsion by angling the rotor disc so that a proportion of its lift is directed forwards to provide thrust.

Jet engines can provide much higher thrust than propellers, and are naturally efficient at higher altitudes, being able to operate above 40,000 ft (12,000 m). They are also much more fuel-efficient at normal flight speeds than rockets. Consequently, nearly all high-speed and high-altitude aircraft use jet engines.

The early turbojet and modern turbofan use a spinning turbine to create airflow for takeoff and to provide thrust. Many, mostly in military aviation, use afterburners which inject extra fuel into the exhaust.

Use of a turbine is not absolutely necessary: other designs include the crude pulse jet, high-speed ramjet and the still-experimental supersonic-combustion ramjet or scramjet. These designs require an existing airflow to work and cannot work when stationary, so they must be launched by a catapult or rocket booster, or dropped from a mother ship.

A propeller or airscrew comprises a set of small, wing-like aerofoils set around a central hub which spins on an axis aligned in the direction of travel. Spinning the propeller creates aerodynamic lift, or thrust, in a forward direction.

A tractor design mounts the propeller in front of the power source, while a pusher design mounts it behind. Although the pusher design allows cleaner airflow over the wing, tractor configuration is more common because it allows cleaner airflow to the propeller and provides a better weight distribution.