wxalex

How do I find out fare routing rules? For example, is it typically legal to fly BNA-EWR-SFO? Is it fair to assume if this routing does not show up when searching United.com it is not a valid routing?

kenn0223

You have to look up the routing rules individually for each fare code (remember the fare code is the longer, usually alphanumeric, code not the one letter fare basis). To do this you'll need access to a GDS (via a travel agent or a tool like ExpertFlyer subscription).

United, and all the other airlines, file fares for specific city pairs. Each filed fare has its own rules which include, for example, if it can be combined with other fares, if connections are allowed and, if so, at which cities, the maximum number of segments, etc. Airlines publish thousands of fares, generally for most conceivable city-pairs in their network. If they don't publish a fare most fares allow for construction so you can put two fares together to get where you want to go. (So for your example, you'd likely have to combine a BNA-EWR fare with a EWR-SFO fare since there is no BNA-SFO fare).

Often the connection rules bake-in some routing restrictions. Here is an example for a BOS-SBA fare:

So in this example, you can have up to 4 connections (indicated by the "-"). I marked each connection set in a different color. You can connect from BOS to one of the Red, Green, or Purple cities however once you are at the Green cities you can only connect to the Purple cites (i.e. if you fly BOS-HOU you can't then do HOU-EWR but you could do BOS-EWR-HOU).

For UA's published BNA-SFO fares there seem to be 4 routing options:

They all look to only allow one connection and HOU looks to be the furthest east they go. It should be no problem to combine a BNA-EWR fare with a EWR-SFO fare. You can likely even book this on the website by using the multi-city search function.

It is NOT a safe assumption to assume that just because you can't get a routing to show up on the website that it's not valid. The best option, if you have a specific routing in mind, is to call UA or a travel agent and have them price the specific routing. If you're just tying to be creative, I am not aware of any website that gives all the valid routings for a city pair (there could be a lot).

What are you trying to figure out?

wxalex

Thank you, that is very informative!