We had a thread about this that got a bit tenuous for whatever reason. It basically boils down to three choices, ordered below in what I think is the most likely to least likely.

- Use the planned new domestic F and premium economy. AS already decided on this seating knowing they were going to expand transcons. However on head to head routes with lieflat they will need to charge significantly less for F. AS currently charges the same or more vs lieflat on SEA-JFK or SJC-EWR (which imo is very similar to UA's SFO-EWR route although others disagree). I think priced right they would fill these F cabins.

- Crossfleet the existing 63 VX A320s on all transcon routes. The VX planes have somewhat competitive F, good IFE, and are more comfortable for longer flights. This would integrate the AS and VX fleets very quickly in a rational way: long flight cool VX plane, short and mid range flight AS plane. However the VX A320 has far fewer seats than the AS 739 (8/12/129 vs 16/24/138) so this would be a financial hit. And it would require adding A320 bases in SEA and PDX.

- Subfleet with a new lieflat F on 737-900 or A321. This would be a couple years at least, and doesn't seem to be the way they would go looking at past AS decisions. However B6 is being super aggressive with Mint so who knows!