Why does the weather cause flight delays or alternate flights?

There are two reasons: first, whether the flight is normal or not is most affected by the weather at the departure airport and the weather at the destination airport; The second is the influence of the weather on the route and the weather in the approach area. Good weather conditions at the airport do not completely mean that the airport is suitable for aircraft to take off and land. Low clouds and thunderstorms covering the approach area of the airport are common factors that cause aircraft delays. Aircraft cruising on normal routes sometimes have to fly around bad weather areas, which prolongs the air flight time and delays flights. For example, in a thunderstorm area, in this case, the takeoff plane can only wait on the ground. Although the meteorological department of civil aviation will rely on advanced equipment to continuously issue more accurate weather change trend forecasts to facilitate flight operation and scheduling, the weather conditions are constantly changing and it is difficult to accurately judge. This will lead to the sudden deterioration of weather conditions when landing, resulting in the inability of the plane to land. For safety reasons or fuel shortage, the plane will have to alternate to other airports. In addition, because different airlines use different types of aircraft, and the take-off and landing standards of different types of aircraft are different, they will appear under the same weather conditions. Some different flights can take off and land, while others are waiting. Many passengers have encountered this situation: the plane broadcast said that there was airflow ahead, and passengers should fasten their seat belts to prevent accidents, but passengers could not see a cloud from the window. That's because the clear sky turbulence is at work. Clear-sky turbulence and atmospheric jet will cause serious turbulence to the aircraft, make the aircraft sink or rise hundreds of meters, and even make the wing load increase and deform or break, which will seriously affect flight safety.