Just an anecdotal evidence: as a US citizen and US lawful permanent resident, was able to board a plane between TIJ and MEX airports with my US driving license only. No questions asked, I didn't have to convince anyone, everybody seems fine with it. Therefore I'm guessing a U.S. passport card is ok too (preferably to be confirmed with someone else).

Just an anecdotal evidence: as a French citizen and US lawful permanent resident, I was able to board a plane from TIJ to MEX airport with my US driving license only. No questions asked, I didn't have to convince anyone, everybody seems fine with it. Therefore I'm guessing a U.S. passport card is ok too (preferably to be confirmed with someone else).