I guess I'm posting this partly to boast, but also to provide helpful hints to others who may want to try to finagle an extra N. American transcon out of an AONE3.

I was scheduled to fly BOS-ORD-LAX this morning, returning LAX-JFK-BOS on Wednesday, with the LAX-JFK portion being on QF108. My BOS-ORD flight was cancelled due to ATC issues at ORD, and AA rebooked me on a BOS-LAX non-stop. That, of course, would itself constitute a second N. American transcon, although the route is served exclusively by 737s, so it's not so exciting. But I called the RTW desk, and without any problem got them to reroute me BOS-JFK-LAX, with the JFK-LAX portion on a 762.

I have similar luck changing YUP fares, which also book into A inventory, but which are supposed to be ineligible to fly on three-class 762 service between JFK and LAX or SFO. I was flying HNL-ORD-BOS, and went to the ticket counter at HNL. They agreed to change me to HNL-LAX-JFK-BOS without any difficulty. Sure it was an extra flight, but it did get me in the F cabin of the 762 service from LAX-JFK.

My recommendation for anyone traveling on paid A inventory fares, it certainly is worth checking at the airport to see if you can be switched to 762 flights between JFK and LAX or SFO. You can't book these in advance, but based on my experiences, airport personnel seem not to have a problem putting you on these flights if the A space is available.