an easy solution to all of those "cash only" people like my dad who refuses to get a bank card or credit card. is to get one of the reloadable prepaid credit cards at walgreens. it costs like $6 to initially get the card i think but after you purchase the card you can reload it by paying cash at a Walgreen's. so now every time he fly's he goes and loads like $20 on the card so if he chooses he can purchase an adult beverage or food on board if he's not lucky enough to be cleared into the first class cabin.
here is a link to a website for one of the cards i was talking about. there are several different companies offering these though greendot is not the only one.
http://www.greendotonline.com