Originally Posted by TrayflowInUK
Tracon, you're suffering from the "HIP check". If the fare you are interested in is an MPM-based fare, that is, one based on a maximum permitted mileage, stopovers are calculated based on the most expensive routing. E.g., if ICN-YVR is more expensive than BKK-ICN-YVR, then the fare will be priced as ICN-YVR.
The OZ fare is an example of this.
However, other fares, such as the NW fare, are routing-based. As long as you follow the routing allowed in the fare rules, stopovers are free, unless the rules state otherwise (some rules say "no stopovers" while others say "stopovers allowed a $x/stopover").
This post is true-ish.
The HIP check does not price based upon the "
most expensive routing". Instead, HIP check pricing applies only to the fare to/from the HIP.
For instance, assume the CMB-SIN-NRT-LAX fare is $2000, the SIN-NRT-LAX fare is $4000, and the NRT-LAX for is $6000.
If you fly CMB-SIN-NRT-LAX with NRT stopover then the fare is $6000.
If you fly CMB-SIN-NRT-LAX with SIN stopover then the fare is $4000.
If you fly without stopver, the fare is $2000.
Further, not all routing-based fares allow free stopovers and waive HIP check. In fact, most do not. Have a look at
this post in this thread.