With so many airplanes flying through an airspace, how do pilots know when Air Traffic Controller (ATC) talks to them? Maybe they just say their names like “Bob…can you hear me?“. But of course, if two Bob’s are in the same airspace then there is a problem. So, the solution to the problem is that we need some specific “names” to know who is calling who.
The easiest choice is the airplanes registration number, just like your car has a plate, the same goes for an airplane.
Another way to do it is to have an allocated name for each airline.
Some examples are:
British Airways: “Speedbird“
American Airlines: “American“
United Airlines: “United“
Now again the problem arises, what if 2 British aircraft fly on the same airspace? how do we know which one is which? The answer is the allocated flight number.
Examples “Speedbird 123“, “Speedbird 141” …
How do pilots know their call sing? Its printed on the flight plan, the paper that describes the route, the purpose of the flight etc