I don't view their plan as pointless at all. Attempting to document an "average" airline passenger is an interesting social exercise I look forward to reading about. I've recently flown to Germany and Japan from the USA and met extraordinary people along the way.
Also, the added effect to our planet by having a plane that's going to fly regardless carry 2 additional people (plus the weight of their luggage) is minuscule at worst.
Documenting the "average" airline passenger couldn't be done from an airport?
As for "The World Without Us", I'm confident that the world will continue to exist even if it's uninhabitable for humans. The issue is preserving conditions favorable to human survival, i.e. having a functioning ozone layer.
Why do you think that the plane is going to fly regardless? If there are 100 people on a plane you're causing 1/100 of the environmental damage. It's true that in 99 of the 100 cases there is no extra plane flying, but in 1 of the 100 cases there is an extra plane flying just because of you.
Also, the added effect to our planet by having a plane that's going to fly regardless carry 2 additional people (plus the weight of their luggage) is minuscule at worst.
I suggest a reading of "The World Without Us" by Alan Weisman for a look at just how durable our planet is. (http://www.amazon.com/World-Without-Us-Alan-Weisman/dp/03124...)