Bernie: "Dear Jan, thank you for your question. When you are driving along in the car with your parents, they follow the road signs and drive on predetermined roads. There are no visible streets or signs in the sky - so how do pilots find the way?
Basically, there are two possible options: Visual flight and so-called instrument flight. Visual flight quite simply means that the pilot orientates himself on the things he can see outside of the airplane, i.e. trees and mountains. Of course, he can't fly through clouds when flying in the visual flight mode, because he wouldn't see anything and that could be very dangerous. Visual flight is also not suitable in bad weather conditions or at night."
Lexi: "Instrument flight is used for all of the big airplanes carrying passengers. "Instruments" means the many practical devices in the cockpit. They show the pilot at all times the position of the aircraft and the route he has to follow. You are no doubt familiar with the GPS device in a car. The pilots use pretty similar navigation systems. They show the path the pilot has to take very accurately.
The pilots are also supported by air traffic controllers on the ground: Among others, the latter make sure that enough distance remains between the aircraft. Furthermore, they are responsible for ensuring that all of the airplanes can take off and land safely. For this purpose, they remain in constant radio contact with the pilots."
Bernie: "Incidentally, even if you can't see them: There really is a sort of "motorway in the sky", called air routes. The worldwide network of air routes is laid down by different points. Even if it is not visible like the street in front of your house, the pilots have to stick to their route and can't simply choose any old path they please.
As you can see: Even without traffic signs, air traffic is clearly regulated so that you always reach your destination safely!"