With so many airplanes flying around, how airports around the world able to track so many airplanes and prevent them from colliding with each other? Is it basically, “alright, so this plane is coming from this route, do not put any plane on this route”?
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More or less. Every airport has a traffic controller whose job it is to coordinate different planes operating around it. A typical airport has “lanes” that planes join until cleared to land or that they follow after takeoff.
Away from an airport, the sky is just so big that there’s not *that* much coordination required. There are a matter of a few thousand flights in the air in the US at any given time – let’s say 5,000 for a nice round number (the FAA says that’s [close to peak activity](https://www.faa.gov/air_traffic/by_the_numbers/)). Dividing the area of the continental US by that number tells us that each plane has an area [about half the size of Rhode Island](https://www.wolframalpha.com/input/?i=3%2C119%2C884.69+square+miles+%2F+5%2C000) to itself. So there’s not much risk of a collision, particularly when you keep in mind that they also have a mile or two of vertical room to play with (and once there’s only a few planes around, a pilot can reasonably keep track of them all).
Air Traffic controllers (see the movie Pushing Tin). Each airline has its own callsign which gets displayed on radar screen. Each controller would be in charge of directing certain number of flights.
There are also certain air routes and altitudes that planes fly at, depending if they are heading east-ish or west-ish, they will have different 1000′ separations.
Planes now also have collision avoidance radar and procedures in case something goes wrong. Sometimes a private pilot might accidentally stray into an airline route.
Firstly there are rules which help airplanes seperating. For long distance flights airplanes have to keep an even or odd flight level depending on if they are going east or west. For airports there are standard arival and departure routes in addition to a standard landing or takeoff flight pattern. So in a perfect world airplanes following these rules should never come near each other. Airplanes also have collision detection systems to detect if they are on collision course, in addition to two pilots looking out ahead for other airplanes.
Air traffic control centers are just there to make sure the traffic flows smoother and tell the pilots to take action long before they have to. The system they use is largely based on timeslots on routes. So for example a route might allow one airplane ever ten minutes so the airliners will apply for one of these timeslots and make sure their airplane passes through the first checkpoint at the time they say. This is usually decided hours before. However it is possible for the air traffic controllers to move around a bit on the timeslots if airplanes does not make their scheduled checkpoints or if the weather changes. If an airplane is too early they can be told to go into a holding pattern, basically fly around in a circle, until their slot is open. Or if there is an open slot before their scheduled one they are routed directly through, possibly even allowed to take a shortcut from the standard routes.
Airspace is divided up by region and altitude. Wherever you are, there is a controller responsible for you. He has the plane on radar and gives you instructions to keep you separated from other planes. The airspace isn’t just an empty system, it has agreed upon fixed points between which you navigate. You will get instructions like “head to XYZ and hold” to get you out of a possible conflict (“hold” meaning that you loop around that fixed point). Or the controller puts you on a different altitude to avoid conflict.
The air traffic control system, aviation is one of the most heavily regulated industries ever. There are many ways that planes avoid each other, there is ATC (air traffic control) which in basic terms tells us pilots, what to do, it’s their job to handle us. In the ATC network, there are several controllers with different roles. A clearance controller approves and clears us to our destination via our flight plan, this is the first controller we pilots talk to. A ground controller which instructions on how to taxi to our destination within the airport, whether that be the runway or the terminal. The tower controller, which handles aircraft taking off and landing, tower controls all movement on the runways. An approach and departure controller handles all incoming traffic and sequences them for arrival and/or handles departing traffic and sends them on their way. Finally, there are ATC centers which are large pieces of controlled airspace that guide us on our way to our destination during cruise. Of course, we also have what we call ‘see and avoid’ if you see a plane avoid it. Finally, most modern-day aircraft have a traffic collision and avoidance system (TCAS) which will send an aural warning to both planes, plane A will receive a warning to climb and plane B will receive a warning to descend although the TCAS system is primarily backup, aviation is all about redundancy and safety. I hope I answered your question, this is just the tip of the iceberg of aviation communication! Feel free to ask any other questions you may have.
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