This sentence emphasizes the importance of safety factors in aircraft design. No matter in which country or airline design department, safety is the primary consideration. Aircraft design must ensure the safety of passengers and crew under any circumstances, which is the most basic requirement of aviation design. "Safety first" has become the common motto of aircraft design departments all over the world, and it is also one of the core values of aviation industry. In the process of aircraft design, designers need to consider various complex factors, such as aerodynamics, structural mechanics, material science, control system and so on, and among these factors, safety is the most important. Only by ensuring the safety of the aircraft can we provide passengers with a more comfortable and convenient flight experience.