Hyperloop? All-electric high-speed rail? Minimum standards for aircraft emissions? CO2 tax on airline tickets - possibly a cap-and-trade system where every p

Hyperloop? All-electric high-speed rail? Minimum standards for aircraft emissions? CO2 tax on airline tickets - possibly a cap-and-trade system where every person in a country get N-many carbon credits they can trade in a free market to people that want to fly more-often? A problem any of this introduces is that (modern) airline travel still has comparable CO2-per-passenger-mile values compared to driving by car[1], so it’s not fair to say that flying is worst (nor the best) way to travel,]. I understand that, I’m general, we should still prefer people fly to Disney World in the summer than drive - or take a cruise ship - as shipping has the worst emissions-per-passenger-mile due to heavy use of “bunker fuel”. [1]According to Wikipedia’s page on aircraft economy. Ctrl+F for “comparison to ground transport”.