xliioper

Booking the two segments separately will result in two separate fares (one for SAN-LAX and one for LAX-PHL) which will cost more than the single $301 SUAGZNM3 through fare which covers both segments. You'd get a $133.30 NVAHZNM1 fare on SAN-LAX and a $273.30 GVAKZNM3 fare on LAX-PHL (while there's N bucket open on LAX-PHL, the G fare is the cheapest available fare filing) for $406.60 total. There's no advantage to doing this. You can't split a single fare which covers the entire itin across multiple segments.

It seems you are missing the root cause of this problem. When you use multi-city and specify flights which are a) a valid routing for a single through fare, and b) have valid connection layover times for a single fare (less than 4 hours for domestic), it tries to employ some intelligence and combine the segments on a single fare to give you a cheaper price than if you had booked them on separate fares. The problem is that it is only checking the fare bucket availability on each individual flight leg (which only applies if you are booking them on separate fares). This may or may not match the bucket availability on the married segments which is what it should be checking when combining the flights on a single fare. Again, this only affects multi-city searches (one-way searches correctly check married segment inventory when combining multiple segments on one fare). This issue has been around for a long time and not really sure why they can't fix it. As I mentioned above, delta.com used to have the same issue, but they have completely turned off the intelligence to combine multiple segments on a single fare when using multi-city search. If you try to specify a particular routing on delta.com for which there are valid through fares using multi-city search it won't even show any options that have a connection less than 4 hours and will only book you on separate fares for each segment. Clearly this is non-optimal behavior and just represents a quick hack that does not actually fix the issue.

Dave Noble

That is an example where the through fare is cheaper. There are plenty of cases where A-B plus B-C is cheaper than A-C via B , either simply due to fares offered or married segment availability only providing for a more expensive booking class for a through journey vs separate segments

xliioper

Fewer and fewer cases of this these days. The legacy airlines have gotten smarter with the fare filings and fare combination rules. AA has separate fare filings for SAN-PHL non-stop vs. SAN-PHL with a connection. The cheapest AA one-way main cabin fares on SAN-PHL non-stop (where AA has a monopoly) is $425 while AA fares that involve a connection are as cheap as $235 one-way in main cabin. It's unlikely you will find a broken fare combination cheaper than that. Also, if you are upfaring from BE to main cabin, you will get hit with two $35 surcharges on a broken fare instead of a single $35 one. There's a broken fare option for SAN-MIA-PHL (MIA is not a valid connecting city for any thorough fares on SAN-PHL. If the connecting city is valid for a through fare, they won't let you broken fare it on a single ticket unless the connection is over 4 hours -- you can get a shorter connection if fares are booked on separate tickets) for $181 one-way in BE, but if you upfare to main cabin it goes to $251 since you need to pay the $35 upcharge twice.

PHLondoner

I came about it honestly. I saw the two flights that I had wanted on a standard one-way fare search a few months ago. And when I went back to check out the fares again recently I simply didn't see the itinerary I wanted (it was placed way to the bottom of the search list for some reason - where I would later discover it) and assumed that maybe they had changed flight timings since it is, in fact, a really tight layover (some forumers over on the LAX thread cautioned against it). So I for fun did the Multi-City search just to see if any timings had changed - and saw the lower fare then.

Anyways, do better AA.