Any travel in one direction only: to a place or back from a place.
To go from one place to another, airplanes can’t fly just any route; they need to respect defined pathways, known as airways. They are established in space by a series of navigational aids, which are used by the aircraft’s onboard navigation systems.
Basically, they are responsible for the air traffic: they maintain the safe, orderly and expeditious flow of airplanes in the air and at the airports, granting pilots authorizations, providing instructions and the necessary information.
It takes place when an airplane needs refueling or to make an unexpected repair before arriving at the final destination. No traffic is unloaded or loaded during a technical stop.
It replaced the compass, serving to indicate the airplane’s path. It’s a very precise instrument that manually aligns with the magnetic compass in the beginning of the flight and shows the direction the aircraft needs to take to arrive at its final destination.