Not sure the numbers on this site add up. Passenger flights are up to around 8 passenger miles per kg CO2 (https://en.wikipedia.org/wiki/Fuel_economy_in_aircraf

Not sure the numbers on this site add up. Passenger flights are up to around 8 passenger miles per kg CO2 (https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#/media/File:Aviation_Efficiency_(RPK_per_kg_CO2).svg https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#/medi...). At these rates and a great circle distance of ~8000km you'd get 4 metric tons for two people round trip. Long-haul planes are likely more efficient than average per passenger mile, so some SFO-LHR round-trips are actually closer to 1 metric ton per person. Still not great, of course.