Airports have oodles of rules that aren't really helping anyone, but here's a humdinger you might not know: some airlines will not accept cash for purchases at certain counters. You know, that stuff that literally says, "THIS NOTE IS LEGAL TENDER FOR ALL DEBTS, PUBLIC OR PRIVATE"? Airlines, man. They don't care, and they don't have to. But let's have poor befuddled Delilah Cassidy pick up the story from there.