Need a drink, snack, headset? If you're on an international flight, you should be okay. If you're on a domestic flight, you better get out your credit card or debit card. American Airlines has joined the list of airlines that require a credit or debit card to pay for purchases onboard.
Other airlines that don't take cash include AirTran, Alaska Airlines, Midwest Airlines, and Southwest Airlines. United Airlines is rumoured to be joining the list.