MHT is the land of Continental Express (and occasional CoCo). All ERJs (and sometimes Dash 8-400s) to EWR/CLE.

Even post-merger, it's not that enticing - ORD is 3x CRJ-700 (18 daily F seats) - down from the days of multiple 757s on that route; IAD is all CRJ-200/ERJ-145s.

If going to Asia, Delta is probably the best bet if you're looking for upgrades on the domestic legs. At least with COUA, you have the option of going over ORD and IAD as well.