A pittance of a tax won't reduce carbon emissions. Depending on where it goes, it might maybe make other means of transportation a bit nicer.

To actively reduce carbon emissions, you'd have to actually make the cost of a short flight much more expensive.

Also, since not all flights can be replaced with lower emission travels (long, intercontinental flights), you'd have to tax them out to the point that people simply stop coming to Europe.

You might maybe get a half of a percentage of global CO2 emissions cut that way. Maybe. In either case, the current growth rate of emissions far eclipses that, so it is at best virtue signalling. At worst, you are punishing poor people for being too poor to afford the high rates, while at the same time bringing in less tax revenue because only a few rich people are flying.