When the global community (or perhaps the larger powers) get real about cutting emissions, one of the "low hanging fruits" will be aviation. How can one argue that my vacation in Thailand (from Canada) or the arrival of fresh tulips and other things overnight from distant places is not a luxury we could do without to save our societies?
With aviation "accounting for approximately 3.5% of emissions from developed countries", and with the additional nitrogen oxides emissions and contrails "estimated to be about two to four times greater than those of CO2 alone" it will be a low-hanging juicy target that is growing at 9% per year.
The options are batteries (for take-off), biofuels and perhaps hydrogen. All of these add to weight and/or cost, are nowhere near ready for general usage, and may have highly questionable net-carbon emissions (just like the EU has discovered with much biodiesel). We also have the case of US corn ethanol which has an EROI hovering around 1, simply a subsidy to US corn farmers. Only Brazil is able to produce ethanol (sugar cane based) at anywhere near an acceptable EROI. For hydrogen there is also the emotional (and practical) issue that was encapsulated by the Hindenburg. Hydrogen is extremely flammable, and therefore the general public would need to be brought around to flying in a "hydrogen bomb".
My personal feeling is that we simply end up flying a lot less (especially on long-distance "cheap" vacations), possibly reinvigorating some of those more local resorts, with flying returning to being more of an elite pass-time.
https://www.bbc.com/news/science-environment-11707135