In a highway, any car can enter and is flexible to switch lanes and the coordination between cars is mostly a responsibility of the drivers. In the railway everything is pre-routed and no surprises are technically possible — dispatchers and planners have more control than the train driver and there is no room for flexibility — you just stay in your rails. What is air like? Can I build my own plane and just join the air traffic without telling anyone?
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Aircraft have to file a flight plan that indicates the route they will travel on. Usually the flight plan is made based on things like how short the route is, what the weather looks like, and if they have to fly around any restricted areas (like you can’t fly over Area 51 in your Cessna). In the US, rules about what paperwork to use and where to file it are made by the Federal Aviation Administration (FAA).
So in this respect I suppose it’s more like a railroad system where everything is pre-scheduled, although there are deviations, like when a flight crew is late to a plane or there is a technical issue. An airport is not going to make all the other flights wait five hours just because one plane needed to recharge its batteries or something.
Not really like either. Traffic is segregated by altitude with East bound traffic is at odd thousands of feet altitudes and westbound traffic is at even thousands of feet altitudes. Navigation is often done by flying from VORTAC point to VORTAC point, but modern nav equipment can give you a direct route. Flight plans are filed before you take off for commercial flights, but the route can be changed in flight if the weather has become a problem. You change by talking to air traffic control and telling them what you want to do and getting permission to do so.
It depends. There are a lot more “lanes” in the air then on the railway, or even highways. So the basic rule is that airplanes can go anywhere they like as long as they do not crash into each other. But it is a good practice to call out on the radio telling everyone where you are.
However that does not work for areas of high congestion such as around cities and airports, at higher altitudes where airplanes go too fast to see others before it is too late, or in bad visability such as clouds, fog or rain. So in some areas any pilot needs to talk to an air traffic controller before entering and while manouvering. There are different classes of airspace and different types of flight following. Sometimes the air traffic controller just tells the airplanes about other airplanes nearby and other times the air traffic controller is telling the pilots exactly where to go. However the pilot is still ultimately responsible, normally the pilots will tell ATC where they want to go and the ATC will tell them how to get there.
For places of extremely high congestion though, such as runways and certain air coridors, there is a need to ask permission. And there might be a long queue to get this permission. So before any flight the pilot will file a flight plan and get slots assigned. That means they need to be at the certain place at the certain time to avoid overcrowding. This is to prevent situations where all airplanes come to the same airport all at once wanting to land so everyone have to circle for hours. One of the most crowded air coridor is the transatlantic flight coridors which are places that due to weather conditions that day is the optimal way to fly across the atlantic. And because of the long distances without radar coverage or good ATC communications airplanes have to be quite far apart which does not help.
Commercial airlines usually follow “airways” that can be thought of as highways in a sense. These are used to manage air traffic controll of so many aircraft in the sky at once. And as another person pointed out they usually stack your assigned altitude based on the direction you are flying. There are “exit ramps” from the airways where an aircraft transitions from in route to terminal areas and then to specific runways. If you live near a busy airport you can usually see these patterns as you see the jets maneuver in for landing. When I was in aerospace years ago there was discussion about moving towards “freeflight” which is where the jet flies a more direct flight using GPS positioning and sophisticated TCAS systems (collision avoidance). I don’t know if that has materialized. It required a lot of coordination and technical development and I don’t know if it ever materialized.
Both, and somewhere in between. There are two main sets of rules for flight:
VFR — visual flight rules. Small aircraft can basically take off and fly any route they want, whenever they want, without much planning or preparation. Sometimes they don’t even have to talk to anyone by radio. They navigate visually, looking at landmarks and such. However there are “rules of the road” that VFR flights have to follow, especially near airfields, and usually VFR flight is only allowed at low altitude, away from big commercial airports, when the pilot can see the ground and surrounding airplanes. Big commercial aircraft are not allowed to do this.
IFR — Instrument flight rules. Much more complicated. Pilots generally have to file a flight plan saying where they’re going, how they’re going to get there, and when they want to leave. They’re usually in constant communication with air traffic control to follow their plan. They navigate using radio instruments and GPS. The rules are *much* more strict and complicated, but they allow pilots to fly big commercial aircraft into major airports in very bad weather. Pilots need special equipment, training and a specific type of license to do this.
Basically, to use your analogy, small personal airplanes work a lot like cars, big commercial aircraft work a lot more like trains.
It’s like this. Click this, click the button top right marked “World Hi” this shows the airways. There are high altitude airways and low altitude airways. They are also layered at 1000 feet intervals.
https://skyvector.com
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