Currently airline passengers don’t have to pay for their carbon emissions, but I doubt that’s gonna last for much longer (we are in an emergency after all). And I’ve seen elsewhere in this thread that the emissions are likely gonna be somewhere between 5x and 10x of normal sub-sonic flights. The price of this extra carbon emission will probably be something that even affluent passengers will want to skip.

Starting to tax airplane fuel would be an important step towards reducing the CO2 output. Possibly that would trigger a switch to synthetic and carbon neutral fuels.

There will be a global cost scheme for carbon at some point in the future. I hope it will be a simple tax (imposed by each state by some international agreements; although some weird cap-and-trade scheme with limited effect is probably more likely given how governments are behaving) and I wouldn’t be surprised if it is mostly in effect by the time Boom plains are in commercial operations.

Whatever the scheme there will probably not be an exception for international flights (I’m guessing countries will be focusing their efforts on exempting their militaries). The thing is that every industry is going to try to get a discount, and that is simply not possible (we are in an emergency after all). So it doesn’t matter if it only shaves of 0.3% of global emissions (which honestly would be a disaster and not acceptable in the long run). What matters is that all industries (except the arms industry; lets be realistic here) will have to suffer equally for their sustained pollution.