Since there are no fixed airways, air traffic controllers determine airplane flight routes by using charts that separate aircraft by five miles laterally and 1,000 to 2,000 feet vertically. Control centers publish and update these charts every four weeks to coincide with the Aeronautical Information and Regulation Control cycle.
Each airway starts at a waypoint, passes through some intermediate points, and ends at another waypoint. Pilots must report to the control center when they pass through certain waypoints. Since airways join or cross at these waypoints, the Federal Aviation Administration ensures that planes do not collide by issuing safe separation standards. FAA requires control centers to separate airways by five miles laterally and 1,000 feet vertically.
When an aircraft takes off, it follows a departure procedure that allows it to join an airway in a coordinated manner. Aircraft must also follow arrival procedures and timings before landing to avoid a collision on the runway. Air controllers ensure that planes follow predetermined routes and procedures by passing radar vectors, speed adjustments and altitude assignments to pilots.
Air traffic control centers construct flight routes by using standard departure and arrival routes. The standard procedure involves setting intervals of 10 degrees longitude and 5 degrees latitude and feeding them into computerized flight planning systems.