Well, the energy inefficiencies in aviation are staggering.
It's taken 50 years of jet travel and APU-equipped aicraft to come to this (Delta starts using it this year) - you'd think that'd be day one that would have been sorted out, but no:
WheelTug plc
Regular long taxis with all engines running, complicated non-GPS approaches following antiquated flight paths that waste millions of gallons - the list goes on and on.
It's just
very, very backwards and slow. I mean, the C152 I fly has 12.000hrs on it and was made in the early 70's.
Only in aviation.