I found this data[0] care of The Guardian regarding pollution created per passenger mile. The GP said fuel per mile but the GGP was talking about pollution. It’s from 2009 so it’s likely in the right ballpark but not 100% accurate given the model of plane they used (737-400) has been largely replaced with newer/denser/more efficient models (737 Max 7/8/900 series) as have cars gotten more efficient. Basically, if you drive an SUV or high end sports car, you’re in the same ballpark as a full plane. If the plane is half full or you drive a small car, the car wins per passenger-mile (or km in this case).
Aircraft fuel efficiency has gotten dramatically better since 2009. Utilization is over 70%, wingtips added 3% fuel efficiency, plus slightly slower fights, and many older aircraft where retired during the spike in fuel prices.
