Well, I need to fly in two directions, not just one FJ is indeed booked for the outbound trip, but CX was my desired return.

Here's how it went. Originally was trying to book SYD-HKG-JFK in J, which showed up on AA and AS as available. This would always error out at the payment step. Looking at the SYD-HKG availability for the same date on BA right now, it shows no J seats available, so this makes sense. PE however had 6 seats open on both legs (though BA would claim there was no end-to-end availability), so we booked that. The "Thank you for booking online at alaskaair.com. Your confirmation receipt will be emailed shortly." email came through before the confirmation page even loaded on the site.

About 20 minutes later, the full confirmation emails arrived. At this point in time, trying to view the trip on Alaska's website would still error out. Half an hour later, 3 more identical confirmation emails came in. Trip would still error out. Then I decided to go to Cathay's site and enter our info and pick seats. Boom, immediately everything was fine on Alaska's end. You could chalk this up to coincidence, but… I did notice later that the first leg was not showing as confirmed, but by that point we had already nuked the res (see next) so it was a moot point.

The next day, I realized that there was J availability from MEL. Same story on BA's site — only if you search for the legs individually. AS showed the seats as available as well. So, we changed the PE itinerary from SYD to a J itinerary from MEL. Or tried. What happened was the old itinerary was gone and replaced by a MEL-HKG itinerary with the onward leg nowhere to be found. Got no email confirmations and the trip could not be viewed online either.

We called reservations and happened to get an agent who actually knew what Cathay Airlines was. She was able to see the entire new itinerary and said that the second leg was waitlisted. Tried to push it through and didn't succeed, but said it should be straightened out in 24 hours. Then (!!!), she called us back about an hour later and told us about the phantom availability, how it's a recent issue, and that the partner desk is trying to escalate it. Her update was that it could take up to a week to resolve this, but that if it fell through, we would not lose our PE seats (not sure how this is supposed to work).

Later in the night, the trip was now viewable on AS's website but still had only one leg. This morning, I took the CX booking code and pulled up the res in their app. It showed both legs as confirmed and ticketed. Went back to the AS app and immediately the trip gained the second leg. It thinks we're in economy, but CX says it's business and let me pick business seats for both legs. First leg is in U, second leg is in I.

Oddly enough, BA shows decreased J space on our flights but only by 1 (used to show 3, now shows 2).

My takeaways are as follows…

• don't bother using BA's website to search end to end availability; just do individual legs
• viewing the itinerary on CX's website seems to somehow tickle the reservation systems into doing something
• good agents do exist!
• good luck to all. i'm sure glad i'm not trying to piece this together for a flight in the next two weeks