Airplanes are not &quot;insanely efficient&quot; when it comes to greenhouse gasses.  A plane emits roughly the same amount of greenhouse gasses per mile per person as a car.  Maybe 50% if we assume an efficient plane and an inefficient car.  And the number of miles travelled by plane is typically much more.  Even one round trip flight from SF to europe is 10,000 miles, which is comparable to a year&#x27;s worth of driving for one person.