Before the plane even takes off, the route plan is submitted to the local Network Management Operations Center (Eurocontrol for Europe, FAA for the USA, etc). There, it is run through a system to check if it obeys all airway rules. If it does not, they will communicate with an airline to correct it. Once the plan is approved, the plane is fueled and loaded, while waiting to get permission from the company dispatcher and ground control to proceed. Ground control navigates the plane to the runway, where it becomes the responsibility of the tower and is cleared for takeoff.

When a plane takes off, the only obstacles in its way are other planes. To make sure there is no possibility of collision, there are certain rules pilots must follow, with the help of an ATC operator. There are three things an operator can instruct the pilot to do - change speed, altitude or direction. For this, they need to know the aircraft's location, using the radar. Radar is continuously sending radio waves into the sky. When they bounce off an aeroplane, the antenna detects the signal and calculates its position. This data is then transmitted to the ATC tower and displayed on operator screens.
Since airspace is usually very complex and busy, controllers need to know their structure well. That is why it is both horizontally and vertically divided into zones, each having its own sets of personnel.

Despite this, we all know that flights experience many delays. Those may be caused by the lack of controllers or too busy airspace zones. When a flight receives a delay, it has two options: to wait or to choose another, alternative route. This is done considering all additional costs and time needed.

Now you know how numerous people work together to make sure all the flights arrive at their destination as safely and quickly as possible.