There are many methods for which we can classify an aircraft; some of the classifications are based on the following approach:

• Lighter-than-air
• Heavier-than-air

Based on the purpose:

• Civil aircraft
• Military aircraft

Wing Configurations:

• Monoplanes
• Bi-planes
• Delta wings

Propulsion system:

• Reciprocating engines
• Jet engines

Lighter-than-air

These are types of aircraft which produce lift or floats in air with the use of a gas which is lighter than air. These gases when contained inside a rigid volume displaces the surrounding ambient air. Examples include balloons and airships like Zeppelin.

Heavier-than-air

Heavier than air aircrafts include passenger airplanes, military airplanes, helicopters, gliders, sailplanes, etc. These airplanes are generating lift and produce thrust to fly in the sky.

Based on the purpose

Airplanes are classified based on the purpose as civil aircraft and military aircraft. Civil aircraft includes commercial, passenger airlines or private airplanes. Private airlines are smaller in size than the commercial ones. These aircraft are used for business purposes, agricultural operations, forest-fire fighting etc. Commercial airplanes are passenger airplanes and Cargo airplanes, which fly between city airports to carry passengers and cargo. There are many airlines operating for these purposes. The size of the aircraft varies based on the number of passengers are carried or the amount of cargo it hauls.

Military aircraft

Military aircraft are of combat and non-combat. They are used to destroy enemy equipment. Non-combat aircraft are designed to carry out support roles. Combat military aircraft includes fighters, bombers, electronic warfare and maritime patrol planes. Non-combat aircraft include military transport, airborne early warning and control and reconnaissance and surveillance aircraft.

Propulsion system

Propulsion system is used to provide thrust to the airplane. The engines which are used to provide thrust can be reciprocating type or jet engines. Reciprocating engines are internal combustion piston engines. These types of engines are used in smaller planes.

Jet engines are used in bigger airplanes and have replaced reciprocating engines. Jet engines derive thrust by ejecting a jet of combustion of air and fuel at a very high velocity. Jet engines can be of turbojet, turbofan, turboprop, ramjet and scramjet. 

Turbojet engines takes ambient air through an inlet, compress to about 10 to 15 times in a compressor and then passed through a combustion chamber where it burns with the fuel. After that, it is passed through a turbine and then to a nozzle with a very high velocity.

A turboprop engine is a jet engine that has a propeller connected through a gearbox. A ramjet is a jet engine with no moving components and is a straight-through duct. A scramjet engine is a supersonic combustion ramjet engine.

Wing configurations

Airplanes can be categorized by the number of wings like monoplane, biplane, triplane, and quadplanes. A monoplane has one wing, biplane, triplane, and quadplanes have 2,3 and 4 wings respectively.

Based on the wing planform viewed from above, there can be straight wings, swept wings, delta wings, variable incidence, and complete flying wing.

Straight wings are earliest wing design which are a straight structure from its fuselage.

Delta wings are triangular in shape. Swept wings are angled backward or forward from its fuselage.

Variable incidence wings can vary the angle of incidence of the wing during its flight.

A flying wing is a tailless aircraft, which has fuselage highly reduced or absent.