Air travel is already quite efficient. If we break it down per passenger, the gas mileage is around 50mpg. Cutting total flight distance only cuts the amount of time that the aircraft is in it's most efficient travel regime (high level cruise). With no corresponding change to the amount of fuel used to climb up to cruising altitude.
Adding extra days to every trip is not cost free. Mode switching for travel is also not cost free. Creating gigantic airports at the nearest points between continents etc... Large scale, expensive and difficult to coordinate changes; which are trying to squeeze more efficiency out of an already optimized system.
Don't mean to sound overly critical, these are interesting ideas on systemic change.
Adding extra days to every trip is not cost free. Mode switching for travel is also not cost free. Creating gigantic airports at the nearest points between continents etc... Large scale, expensive and difficult to coordinate changes; which are trying to squeeze more efficiency out of an already optimized system.
Don't mean to sound overly critical, these are interesting ideas on systemic change.