737-400s on Transcons?
 

I was poking in the schedules for July 21 and noticed the 734 on EWR-SEA - seems odd because I thought AS was flying only the -700/800/900 on flights east of DEN.

Mistake or reality?

Mistake, I imagine.

With a range of 2,370 miles (and unknown what the load/cargo factor needs to be to do it), she can't make the ~2400 miles for SEA-EWR and is just at the outer range for SEA-IAD/DCA (at ~2300 miles).

Alaska puts that information in the system on a tentative sort of basis. In other words, we all know they will use one of the 737 NG's for the transcons but they've yet to finalize the schedule for that period so they temporarily call it a 734. It will be corrected down the line.