What is air traffic control?

There are two kinds of delays before the plane takes off, one is due to airlines and the other is due to air traffic control. Airline reasons include aircraft turnover, delayed crew and aircraft maintenance. In short, the plane or crew didn't arrive at the airport on time/get ready for takeoff. Air traffic control means that the plane has all other takeoff conditions, but the tower won't let it. There are many reasons for not letting go. There are three kinds of weather: departure airport weather, destination weather and, most importantly, airline weather. Bad weather (heavy rain, fog, thunder and lightning, strong wind, etc.). ) Not suitable for take-off and landing and flying. One of them can't fly in bad weather. China's airspace is completely under the air force's control. The air force will use 20% of it for civil aviation (it can be recovered at any time). In this 20% space, some routes have been set up. There are requirements for the front, rear, left and right distances of aircraft on the route. There are too many planes on the same route to allow new planes to fly in, otherwise there will be safety problems. Military activities. As mentioned above, the air force gave 20% of the airspace to civil aviation. The air force needs it, and civil aviation needs to make way. Typical is a military exercise. Then a no-fly zone (usually 300-500 kilometers) will be drawn nearby, and all planes will bypass and the route needs to be adjusted. Runway problem. The airport runway may need maintenance, or something happens on the runway (such as a large number of birds), then the runway will be temporarily closed. With fewer runways, the take-off and landing capacity will be reduced, but flights are arranged according to normal conditions, so extra queuing time is needed. Air traffic controllers also have little to do (except Li Gang on the plane), so they can only wait in line patiently. Queueing is based on closing the hatch (that is, the plane can push out, taxi and then take off). Planes with closed doors can line up at the tower, and they can't line up until they are closed. So airlines don't really want to leave passengers in the cabin when they encounter air traffic control. Because if you don't lock it in the cabin, you will never take off. Of course, not all delays are air traffic control, nor are they claimed to be air traffic control.