Children aged 5- 12 can fly by themselves when applying for unaccompanied children service, and children aged 12 can fly by themselves. In order to ensure the safe and smooth flight of unaccompanied children, children over 5 years old but under 12 years old who travel alone must go through the relevant procedures for unaccompanied children before airlines can accept transportation. Aircraft: refers to an aircraft that is heavier than air. One or more engines generate forward thrust or pull, and the fuselage is fixed with wings to generate lift and fly in the atmosphere. The airplane is one of the most important inventions in the early 20th century, and it is generally believed that it was invented by the Wright brothers in America. Their flight on 1903 12 17 was recognized by the International Aviation Federation as "the first controlled sustained power flight by a heavier-than-air aircraft", and in the same year they founded Wright Aircraft Company. Since the invention of the airplane, it has become an indispensable tool of modern civilization. It profoundly changed and influenced people's lives and opened the history of human conquest of the blue sky.