http://consumerist.com/2007/09/07/american-airlines-announced-that/

American Airlines announced that beginning next week, they will begin testing credit card only flights out of San Francisco. Jet Blue has said that it will stop accepting cash on flights next quarter. Other airlines that already don’t accept cash: AirTran, Frontier Airlines, Spirit Airlines, Midwest, ATA Airlines, Virgin America and Hawaiian Airlines. [Kansas City Star]