# # # I. Definition and Classification
* * * Definition * *: An airplane is a heavier-than-air aircraft that flies in the atmosphere by means of a power plant to generate thrust or tension.
* * * Classification * *:
1. ** Classification by purpose * *:
* * * Passenger aircraft * *: According to the size and voyage, it is further divided into long-range (large) passenger aircraft, medium-range (medium-sized) passenger aircraft and short-range (light) passenger aircraft.
* * * Cargo plane * *: used to transport goods, usually with a large load, with a large hatch or a convertible fuselage, which is convenient for loading and unloading goods.
* * * Trainer * *: used to train civil aviation flight personnel, divided into primary trainer and advanced trainer.
* * * Agricultural machinery, forestry machinery * *: used for agricultural spraying, fertilization, sowing, forest patrol, fire fighting, etc.
* * * Sports machine * *: used to develop sports, such as skydiving, and can be used for mobile flight.
* * * Multi-purpose light aircraft * *: There are many types and uses of this kind of aircraft, such as geological exploration, aerial photography, air tour, emergency rescue, short-distance transportation, etc.
2. ** Classification by engine type * *:
* * * Propeller plane * *: Thrust is generated by the rotation of the propeller.
* * * Jet aircraft * *: Jet engines are used to generate thrust, which can be divided into subsonic, transonic and supersonic types.
# # # Second, the development process
The invention and development of aircraft is an important chapter in the history of human science and technology. Since the Wright brothers successfully tested the world's first aircraft in 1903, aircraft technology has been continuously improved and flight performance has been continuously improved. From the original propeller plane to the modern jet plane, from subsonic to supersonic, the speed, range and load of the aircraft have all achieved a qualitative leap.
# # # Third, important features
* * * Efficiency * *: As a rapid means of transportation, aircraft has extremely high speed and range, and can quickly connect with all parts of the world.
* * * Safety * *: With the continuous progress of technology, the safety and reliability of aircraft have been greatly improved and become an important part of modern transportation system.
* * * Versatility * *: Airplanes are not only used to transport passengers and goods, but also widely used in military, scientific research, agriculture, forestry, sports and other fields.
# # # IV. Future development trend
With the continuous progress of science and technology and the sustained development of the global economy, the aircraft industry is facing new opportunities and challenges. In the future, aircraft technology will continue to develop in a more efficient, safer and more environmentally friendly direction. For example, the development and application of new power systems such as electric aircraft and hybrid aircraft will promote the green transformation of the aircraft industry; The rapid development of UAV technology will bring revolutionary changes to air transport and military operations; At the same time, the application of intelligent and digital technologies will also improve the operational efficiency and management level of aircraft.
To sum up, as an important means of transportation and scientific research tools, physical aircraft plays an irreplaceable role in modern society. With the continuous progress of technology and the sustained development of the global economy, the aircraft industry will continue to usher in a broader development prospect.
