DJ6 has a valid point, but I'm not sure turning his back on in-flight purchases will make a difference.
The rapid advance of cashless transactions, whilst understandable, is a really sinister development. Once Central Banks replace their currencies with digital ones, the damage will be complete. You as an individual will be able to be monitored and controlled through your expenditure. So if Government decides you can only take four flights a year, you will simply be automatically barred from booking a fifth. The same may happen if you try to buy "too much" red meat, or "too many" sugary drinks. If you post something on X criticising the Government, they may prevent you travelling, or buying fuel, or any other punishment they see fit.
If you think I'm scaremongering, take a look at the Chinese Communist Party's social credit scheme, or look at how the East German government monitored its citizens, well before the advent of the internet.
All we can do to combat this trend is to use cash wherever we can, use social media as little as possible, and make sure that, when we vote, we vote for the candidate who really values freedom above all else.