I think the reference was to horizonair the FT member, not Horizon Air the airline. QX has nothing in the fleet that's make SEA-PIT anyway. It'd definitely be an AS run with one of the NG 737s.

PIT hadn't crossed my mind as a new AS station, but it'd be interesting... a shot across USAirways' bow, of course... and it would continue the recent AS pattern of tweaking most majors' hubs as they expand east, but not NW.