I love the question I got recently from Rob who asks:
Paul, What is the origin of the instrument airway routing system and how are the alpha-numerical descriptions based for them?
I liked this question becuase I knew immeadiately after reading it that I didn’t have a clue what the answer was going to be (which isn’t that rare) and that finding the answer was going to be fun, I was right.
I have a couple of email addresses at the FAA that I like to use for questions just like this one and I was AMAZED at how fast the FAA responded with a very complete answer for Rob’s question. I was thinking about editing their email but I’ll just leave it as is in it’s entirety:
The origin of airways can be traced back to the Air Commerce Act of 1926. Airways evolved over the years as new NAVAID technology and instrument flying procedures were developed (For more info, see http://www.faa.gov/about/history/chronolog_history/).
Here’s where we are today:
All airways are established through rulemaking procedures under Title 14, Code of Federal Regulations, Part 71. Rulemaking action to establish or modify routes is the responsibility of the Airspace & Rules Group at FAA HQ. Route numbers are also assigned by the Airspace & Rules Group.
Part 71 was modified in 2003 to adopt the ICAO term “Air Traffic Service (ATS) Routes” as an overall term to identify the U.S. domestic route structure. Specifically, in Part 71, the term “ATS Route” means: Jet routes, RNAV routes, VOR Federal airways, and colored Federal airways (i.e., LF/MF routes).
General information about establishing routes is contained in FAA Order 7400.2, “Procedures for Handling Airspace Matters.” The descriptions of all U.S. domestic ATS routes are published in FAA Order 7400.9, “Airspace Designations and Reporting Points.” These publications can be viewed on the internet at:
The numbering system used varies depending on the type of route.
- For VOR Federal airways (V) and Jet Routes (J), a one to three digit number from 1 – 999, is assigned (V-3, J-591, etc). Even numbers are assigned for routes that extend generally east-west and odd numbers for routes that extend generally north-south. For a new route, the number selection is somewhat random — although we check the National Airspace System Database to make sure the number is not already in use.
- For colored Federal airways (LF/MF), the color names “Amber, Blue, Green and Red” are used followed by a one or two digit number (A-2, G-18,etc). The color indicates the route alignment. Routes that extend generally east-west are designated as Green or Red. Routes the extend generally north-south are designated as Amber or Blue. Note: There are still about 49 colored Federal airways in the system (primarily in Alaska).
- For RNAV routes, the U.S. uses designators (T and Q) and number sets that were assigned for our use by ICAO. The FAA decided to use the T designator for low altitude RNAV routes and the Q designator for high altitude RNAV routes.
- Low altitude RNAV routes (below 18,000′ MSL): “T” plus a number from 200 – 500. – – High altitude RNAV routes (at & above 18,000; MSL): “Q” plus a number from 1 – 499. Note: The same “even number for E-W” / “odd number for N-S,” as is used for V & J routes above, also applies to RNAV routes.
Note: Offshore Oceanic ATS routes are outside U.S. domestic airspace and are not covered under Part 71and are not processed by the Airspace & Rules Group.