United Airlines (aka United Continual) and a number of other US airlines have been cashless on their planes for a number of years. All sales on the planes, for example for duty-free purchases, require the use of a credit card or a debit card.
I recently returned from several domestic US flights on United where I needed to check my bags. The use of the overhead bins and the under the seat space were not options in my case. When I arrived at the airport I fully expected to pay a baggage fee and took cash to cover the full cost. However, when I arrived at the airport lobby I fund that the only way to pay United the required baggage fee (another sore issue with me) was with a credit card or a debit card.
With cash in hand I found that United Airlines had installed several machines, all owned by a third party, to sell me a prepaid debit card. As the debit card selling machine will not make change and cannot be reloaded, it took a while for me to find someone to make change.
In just over half an hour, I was able to get the proper change, put the proper amount of cash into one of the debit card selling machines, get a prepaid debit card, put the debit card into the United check-in kiosk about two feet away, and then discard the debit card in the nearest trash bin.
I rate the exercise: 1) a waste of my time, 2) ecological unsound, 3) probably (?) profitable to all of the parties except me, and 4) rather customer unfriendly. The only 'upside' of the incident was that I arrived early at the airport and I did not miss my flight.