Car carbon emission are usually around the level of aviation emissions with typical occupancy levels [1]. But Air travel encourages flying much larger distances as opposed to e.g. driving. Without air travel, no sane person would travel to e.g. Asia from Europe a few times per year. Flights over 4000km are 6% of flights but around 52% of emission in europe [1]. Few people will drive 4000km with a car.

In my opinion, simply comparing the averages is also not useful. I expect that car occupancy will be higher for distances where flying becomes reasonable, reducing the average emission levels. For example vacation travel most often happens in a group not alone. I also think that the economic benefit of car emissions is higher than plane emissions.

Emissions of air travel are commonly often given as CO2 Emissions (around 2% of emissions worldwide), while the complete warming effects are likely around 4% of warming worldwide [2].

Air travel is very unevenly distributed, with most of the population never flying as opposed to e.g. cars (in germany 2/3 of people fly less than once per year with half of them never flying [3], 12% of adults in the US account for 68% for flights takes [5]. In general look at [6] figure 4). Thus a small portion of the population benefits from air travel as opposed to e.g. car travel.

The increase in flying for developed countries and the further economic growth in developing countries means that without any intervention flying is expected to increase a lot in the next decades and threathen the paris goal.

It's very unlikely that air travel can meaningfully decarbonise in the next decades as opposed to car travel where a broad adoption of electric vehicles is expected in the next decade. The adoption of SAF has been pretty much non-existent up 'till now, contrary to industry promises (and fraught with issues both financial and energy usage) and battery-based solutions are only an option for ultra-short distance flights. Hydrogen based solutions are also very much in the early development phase and IMHO also unlikely to succeed.

Long-distance air travel is also without real alternative and can't be rolled back. For example, as air travel gets adopted more broadly, more people live in other countries a longer distance away and regularly visit their families at home. Trying to revert this is basically impossible (people can't see friends and family anymore), so higher adoption is hard to revert. If the population broadly becomes used to international vacations, reducing them in a large way also becomes unpopular. This is continually increases, so social solutions continually get harder.

Thus we expect to increase flights (but still with uneven distribution), have little hope for technical solutions for eliminating emissions in the next decades and social solutions will get harder as time goes on.

[1]: https://ourworldindata.org/travel-carbon-footprint
[2]: https://en.wikipedia.org/wiki/Environmental_effects_of_aviat...
[3]: https://www.eurocontrol.int/sites/default/files/2021-02/euro...
[4]: http://www.mobilitaet-in-deutschland.de/pdf/MiD2017_Tabellen... page 74
[5]: https://www.sciencedirect.com/science/article/pii/S095937802...
[6]: https://theicct.org/wp-content/uploads/2022/09/global-aviati...