Airliners get 49MPG per PERSON, so even something like a Chevy Suburban, at say 17MPG and with four passengers, gets 68MPG per person. With smaller vehicles, like say a Chevy Malibu at a conservative 28 MPG rating gets 112 MPG per passenger with four occupants.

It gets better with mass transit too, Greyhound states 162MPG per passenger (http://www.greyhound.com/company/media/facts.shtml)

And trains rate anywheres from 250 to 1400MPG! (http://en.wikipedia.org/wiki/Fuel_efficiency_in_transportation)

So, yes flying is an extremely innefficient way to travel, unless you were travelling alone by passenger car.

Assuming that these numbers are calculated only with a driver and that three more individuals lower the fuel efficiency by, say 10%, we have 17MPG. But there are four people riding in the car, so we need to find the equivalent MPG per person. We do this by multiplying the MPG by the number of passengers, for a result of 68MPG/person!

Imagine what the resultant personal MPG’s are for more fuel efficient vehicles out there! There’s no two ways about it, flying and flying at modern speeds especially, is an energy intensive and innefficient form of travel, unless you always travel alone in big SUV’s.

Let’s also consider buses, http://www.greyhound.com/company/media/facts.shtml
Greyhound states a per passenger MPG of 162MPG!

What about trains? http://en.wikipedia.org/wiki/Fuel_efficiency_in_transportation#Trains

Wikipedia references figues from various sources from 300-500 passenger MPG for passenger trains….

So flying IS the least efficient, however these calculations do not take into account the massive amount of infrastructure required for land based travel (especially cars). If you are looking for the most ecological responsible choice, I say go for the train! Best MPG and far less infrastructure required than cars and buses!