Airline partners? Very few, but they're slowly building, mostly smaller airlines in adjacent countries, WestJet for Canada, Volaris or something like that for Mexico.

It's irrelevant to this discussion anyway, because the "loopholes" for earning lots of Southwest awards fast through hotel partners (and most specifically, partners of those hotel partners, like Amtrak), and for doing three-way transfers, are long closed up. And Southwest itself uses Chase.

I only brought it up to point out that one such hotel partner, Choice, would have been churned left and right if BofA had allowed "heavy" churning of the Choice card. But we know (because someone tried) that they didn't. (The deals for transerring to Southwest at great rate only lasted a half year at most, so "slow" churning was of no use to people pursuing those deals, only "heavy" churning would have been.)