Originally Posted by
VegasGambler
Not quite sure what is going on here but right now for SFO-JFK in 2019, the R (main) fare is about $2 cheaper than the fare that books into X with underlying code R.
The bottom line is that there is lots of Main SFO-JFK for $127 (last year's prices!) while the X fares are $129. The main is R; the X is underlying R.
I'm guessing that this is a mistake on AS's part; buy em while you can.
If you look closely at these flights, you will see that the 9:20AM departure and 11:30AM return flights do have Saver fares at $129 one-way and Main(R) fares are $157. The other 3 daily flights do not have any Saver fares and just have $127 Main(R) fares. This is undoubtedly due to B6 who is likely the fare setter on this route and does not yet have Basic Economy fares. There's no B6 flight around 9:20AM, so AS seems to feel they can charge a premium for that particular flight. There is an 11:10AM B6 JFK-SFO flight, but that time slot likely has sufficient demand that AS feels than can compete against B6 with pricier Main fares.