>Flying is a stupid symbolic focus as a "luxury" if you are talking about airlines instead of your own private jet. It has better passenger mileage than cars but worse than a fully loaded bus.

Except you generally aren't taking a car or bus across the country, or to another continent, multiple times a year because you want to check out this zoo or that beach or go attend your friends exotic destination wedding because they found cheap flights during such and such month or because you want to go to Antarctica to see the penguins. Go install a dating app, fire it up and start swiping women 20-35ish, you'll see photo after photo after photo of women with elephants or tigers or at this landmark and that landmark. This sort of travel simply would not exist without airplanes at a ton~ of CO2 per person per round trip.

So comparing planes to buses or private vehicles doesn't really equate. Cheap air travel has opened up far more travel opportunities for pleasure than have ever existed before and air travel is growing year after year. I also suspect that any given passenger's fuel usage might not be as efficient as it seems given most flights are NOT one stop to the destination and routinely involve 1 or more connecting flights which sometimes require you to actually travel past your destination only to have to backtrack on another aircraft.

And for the insane amount of business flights, nearly all of that could be handled via a telephone call or video chat. Take YC they make 'finalist' founders fly out to the bay area to interview in person at a ton or three of CO2 per person round trip when they could just fire up a Skype at a few hundred grams of CO2 per gigabyte.

Except you can't drive 500 miles per hour while you nap, so flying makes it much easier to rack up those miles.