Read the routing rules if you want to maximize your routing. The longer my routing, the more miles I earn.

I will be using Expedia.ca as the default way to find a routing, as it is free, and available to everyone. ExpertFlyer.com offers it paid subscribers easier access to routing rules. Routing rules are also viewable the same way as through Expedia.ca when booking (not bidding for) flights on Priceline.com for example. They are omitted from the fare rules on Travelocity, Orbitz, or most major airfare websites.


Once I price a ticket using the applicable fare on Expedia, I can view the fare rules including the routing applicable.
To do this, I want to find any dates where the fare applies, it doesn’t matter if these dates or routing work for you at this point. Availability is better farther out and better on TUE/WED so I quickly plug in TUE/WED dates as far out as possible until I get Expedia pricing my itinerary with the desired low fare. If step 2 showed my fare was valid through Sept, I would choose Sept dates for the highest chance of finding the fare. If my first couple date queries don’t pull up my desired fare, I would also specify my desired airline in the Expedia search field. Say I am looking for an AA fare. Expedia exhausts more AA possibilities when searching if I have AA specified, increasing my chances of finding the fare. Once you find and select flight options at that fare, Scroll down to Expedia’s “2. Review the rules and restrictions.” One option under this heading is “Read an overview of all the rules and restrictions applicable to this fare.” Click on the “rules and restrictions” link, scroll down, and at the bottom you will see “Routing.”

Understanding Routing Rules

Routing rules include many routes the airline does not fly today. In order to book your ticket, you need to not only identify a valid routing, but a valid routing the airline (or a codeshare partner) actually flies.

“-” means “to”
“/” means “or”
“FROM” means “start with”
“TO” means “Continue with”
Multiple “FROM” or “TO” lines means choose one.
You must use one “from” line followed by one “to” line.
You can skip as many or all of the intermediate cities along the way.
Whatever cities you do not skip in the routing must be transited in the order they appear in the routing.

The airline, beleow AA, between city components specifies what airline must be used between cities. It is the flight #, no the operating carrier. If AA had a codeshare flight number between STL-DFW operated by another carrier it would eligible, because it is an AA flight (operated by someone else).


Example 1:
Let me interpet a sample routing for an AA fare from STL-FLL. The Expedia rules read:
ROUTING 3 FROM STL-AA-DFW-AA-
OR FROM STL-AA-CHI-AA-
OR FROM STL-AA-DFW-AA-RDU-AA-
TO MIA/RDU-AA-FLL*

You can go from STL to DFW on AA
OR from STL to CHI on AA
OR from STL to DFW to RDU
Continue with either MIA or RDU before arriving in FLL.

Possiblities:
STL-FLL
STL-DFW-FLL
STL-DFW-MIA-FLL
STL-DFW-RDU-FLL
STL-CHI-FLL
STL-CHI-MIA-FLL
STL-CHI-RDU-FLL
STL-DFW-FLL
STL-DFW-RDU-FLL
STL-DFW-RDU-MIA-FLL
STL-DFW-MIA-FLL

Example 2:
A US fare from Phoenix (PHX) to Newark (EWR).
Expedia shows:
ROUTING 400 FROM PHX-US-LAS-US-DEN-US-CHI-US-
TO CLT-US-RDU/GSO-US-WAS/BWI-US-
PHL-US-EWR*
OR TO PIT-US-WAS/BWI-US-PHL-US-EWR*

You can go from PHX to LAX to DEN to CHI on US
Continue with CLT to RDU or GSO to WAS or BWI to PHL to EWR on US
OR Continue with PIT to WAS or BWI to PHL to EWR on US

According to this routing, the most segments I could fly would be PHX-LAS-DEN-CHI-CLT-RDU-WAS-PHL-EWR and then back in reverse EWR-PHL-WAS-RDU-CLT-CHI-DEN-LAS-PHX


When the routing rules are more complex, reading them can be time consuming. Take UA’s fare rules from Chicago to San Francisco for example.

ROUTING 2 FROM CHI-
OR FROM CHI-MLI/COS-
VIA STL/MSP/MKC/OKC/TUL/HOU/DFW/
ICT/DSM/OMA/LNK-DEN-
TO LAX-SBA-SNA-SBA/BFL-MRY-SFO*
OR TO BOI-SFO*
OR TO BOI/SLC-LAX-SFO*
OR TO SFO*
OR TO OAK-SFO*
OR TO PHX/LAS/SLC-RNO-SMF-SFO*
OR TO SBA-BFL-SFO*
OR TO SLC-RNO-SMF-SFO*
OR TO SNA-BUR/BFL-FAT-SFO*
OR TO COS/PHX-TUS-PSP/ONT/LAX/LGB-
SAN-SFO*
OR TO PHX/LAS/SLC-SFO*

When I see a routing like this, I will skim looking for the farthest points in different directions and focus on those combined with UA's route network.

I repeat, just because a routing exists does not mean it is bookable. Some routings are not currently flown. If there are no flights operated by or code shared between two cities, they cannot be included in a routing you want to book.

Secondly, many carrier also have a maximum permitted segment rule on their fares. For some US airlines it is 4 flights each way on domestic fares. So just because there may be an eight segment routing between NYC and LAX does not mean you can fly eight segments each way.

Remember, the mileage runner is generally trying to maximize status miles, or in some cases, status segments. So the goal is to determine the longest, yet efficient routing.

So given the option of flying SAN-LGA non-stop, or flying SAN-STL-LGA, a mileage runner would not choose the connection, unless they were trying to accrue segments, for efficiency reasons. SAN-STL-LGA is 2445 miles. SAN-LGA is 2441 miles. Adding a connection to gain 4 miles! No way!

The point is to choose connections strategically. When I fly ORD-SEA-SAN instead of ORD-SAN I earn 2771 miles instead of 1723 miles. A connection for more than a thousand miles is well worth it to me.