For example, from RCTP - ZGGG the route is AJENT MKG A1 ANPOG R200 GLN W22 IDUMA via the AJENT SID to the IDUMA STAR. What does "A1 or R200 or W22" mean? Are they just randomly allocated letters with random numbers for routes?
- RCTP - Taipei, Taiwan Airport
- AJENT SID - Standard Instrument Departure leading to the Navigation fix named AJENT
- MKG - fly to the MAGONG VOR Navigation beacon
- A1 - follow airway A1
- ANPOG - until the fix named ANPOG
- R200 - follow airway R200
- GLN - until the GUANLAN VOR Naviation beacon
- W22 - follow airway W22
- IDUMA - until the fix named IDUMA
- IDUMA STAR - follow the IDUMA Standard Arrival Route
- ZGGG - land at Guangzhou Baiyun International Airport
A1, R200 and W22 are airways. They are defined by lists of waypoints. The waypoints between the first and last used on the airway are omitted and replaced by the airway name, otherwise the flightplan would be extremely long.
As an analogy one could describe a route on the road. For example Frankfurt - Amsterdam could be described as:
FRA - 44 - FRA KRZ - A3 - BORDER - A12 - KNP OUDENRIJN - A2 - KNP AMSTEL- S110 - AMS
Without mentioning all the highway intersections and exits, the route is described in sufficient detail to drive it. The numbers of the highways appear to be somewhat random, but I am sure somebody has thought about how to best assign the numbers.