I don't think an airline would endorse a ticket to another carrier except in irregular operations... it's not something they do "just because." Moreover, I really don't understand your multi-step plan with different cards, since each refunded ticket would go right back onto its original card... original charge minus refund credit equals zero.

But even if this procedure did work, what you are proposing is STILL just as unethical as the first case. When you pay for something on a CC and get refunded in cash, you are effectively circumventing the cash advance rules and are therefore earning rewards against the T&Cs of your card, which you accepted when you signed up for the card. When this happens "by accident" on a small purchase (because the merchant, for whatever reason, gives you cash rather than a card refund) then that's one thing, but setting out to do this intentionally, especially on a large-dollar purchase, is tantamount to fraud. (And this doesn't include the fact that the merchant, the airline in this case, is paying a 2-3% fee to the credit card company for processing your ticket, which they would likely not have sold you if they knew your intent was solely to refund the ticket and earn rewards illicitly.)