"Boom is leveraging advances in engine design that yield greater fuel efficiency, which will mean cheaper ticket prices. But they aren’t stopping there. Boom plans to use fuel made from carbon removed from the atmosphere, meaning that supersonic travel will be carbon neutral from day one."
You can have cheap tickets and don't give a shit about the climate or you can claim you use extra expensive synfuels made from carbon removed from the atmosphere. You can't have both, except if you're talking bullshit.
One way this could work is if we massively scale up renewables. While from a climate perspective you'd want energy to be as expensive as possible as long as there's fossil in the mix, from a social perspective you'd want it to be as cheap as possible. Ideally, all neccessities (power, food, water, transportation) could be made so cheap that everybody can afford them, and they cease to be commodities.
If you produce so much power - think solar on every rooftop, maybe one day fusion or clean fission becomes available - you will neccessarily have some way to store surplus energy. Especially with solar and wind. I can imagine that one way to do that will be synthetic fuel from air or from trash.
So yes, today it is not feasible (with today's technology and society). But I think it is not more unrealistic than other ideas popular around here, like hyperloop, fusion, or self-driving cars.
Fuels made from carbon filtered from the air are expensive. Like... not a bit more expensive, but really expensive.
While there's some uncertainty about how expensive - this is technology that doesn't exist today - it's gonna require massive amounts of energy, which is simple physics.
It doesn't really make sense to make fuels from CO2 drawn from the atmosphere if we're still pumping oil. Instead, make jet fuel from the oil, then make that carbon neutral by capturing and sequestering the CO2. This will change if green hydrogen becomes very cheap, but not yet.
Even today's airline industry is unsustainable and can only continue to function because it's heavily subsidised.
Fossil fuel for airplanes is tax-free and cheaper than petrol, e.g. $3.31/gal w/o taxes in California [0] vs. $2.06/gal (average) for jet fuel [1].
Using atmospheric carbon to generate fuel is significantly more expensive than that as even just capturing the CO² costs more than the crude oil used for jet fuel [2].
The claim of "carbon neutral fuel" basically rests on super optimistic assumptions already. The cost can only be competitive if a world-wide carbon tax on the order of $200/metric ton is implemented, which is very unrealistic.
You can have cheap tickets and don't give a shit about the climate or you can claim you use extra expensive synfuels made from carbon removed from the atmosphere. You can't have both, except if you're talking bullshit.