86 years ago today, on August 27, 1939 (July 13, 1939 in the lunar calendar), the world's first jet took to the sky. On August 27, 1939, the world's first jet took to the sky. This aircraft was made in Germany. Jets are different from other types of aircraft, which rely on jet engines to push the fuselage forward. Jet engines use the reaction force generated by the high-speed gas stream ejected by the engine itself to propel the aircraft. This principle was used by people in ancient times in our country. The rocket with gunpowder invented in the Song Dynasty used this principle. There is a paper tube on the rocket, which is filled with gunpowder. When the gunpowder burns, a strong jet of air is produced from the tail, and the rocket can move forward rapidly by using the reaction force of the jet stream. However, it was only in the early 20th century that people really understood this principle completely. The Russian scientist Tsiolkovsky's book "Studying Space with Jet Tools" published in 1903 clarified the theory of rocket flight, discussed the possibility of using rockets for interstellar transportation, proposed the idea and schematic diagram of liquid fuel rockets, and completed the calculation of the world's first jet engine. These provided the theoretical basis for the manufacture of the jet aircraft. The birth of the jet aircraft is a major event in the history of human transportation. It can fly more than 1,000 kilometers to more than 3,000 kilometers per hour, high-energy flying to an altitude of 20,000 to 30,000 meters, and the farthest one can fly continuously for more than 10,000 kilometers. It has made a major leap in human transportation speed.