Originally Posted by
mherdeg
This would avoid the OP's confusion ("why can't I buy a G fare? it says there's G") but would be really, really bad for other people because it would make it quite difficult for them to see whether there is G inventory on a segment where it is important to them (for the kinds of reasons you outline above).
This question pops up at least once a month, and is one reason that there is now a warning if you go to enable Expert Mode in your profile. There are many reasons those of us who know what we're doing want the website to display all booking classes regardless of whether there is an available fare, as you've pointed out.
United.com Expert Mode
Expert Mode is a fare class availability feature designed to help our most experienced travelers with the planning process. This feature is intended for informational purposes only, and may not always match our exact availability or reflect the stages of our upgrade processes.
Please keep the following considerations in mind when using Expert Mode:
This is not a forecasting tool. Availability levels in certain fare classes should not be interpreted as indicating that we will make other fare classes available.
The presence of a particular fare class does not mean that there is a fare associated with it. For example, we may offer availability in a discounted fare class, but that does not necessarily mean we have published a fare that corresponds to it.