The fare rules for AS LAX-SFO fares specifically exclude AA codeshare flights and do not permit AA flights (see the flight application section) --
THE FARE COMPONENT MUST NOT BE ON
ONE OR MORE OF THE FOLLOWING
AS FLIGHTS 4000 THROUGH 8999.
This means the only way to combine the flights on a single ticket are with a broken fare (an AS fare on SAN-SFO and an AA fare on the LAX-SAN segment). However, AA fare combination rules only allow the fares to be combined if you have a full Y fare (YA2AA). It's that full Y AA fare that is what is blowing the price out of the water. The combination rules on the AS fares are not as restrictive and the AS fare on the SAN-SFO segment is far more reasonable. Yes, it's pretty silly to present such options, but now you know why it is pricing out the way it is.
Last edited by xliioper; May 11, 2019 at 9:12 am