> The Henwoods (and Heartfields) who fly commercial jets are
> contributing significantly less than someone in a private jet.
Not for long, though. Private jets tend to be newer and more efficient than airliners. New airliners can even be more efficient than a Prius:
http://www.easyjet.com/EN/News/too_dirty_to_fly.html
"Governments and regulators must begin to recognise that some aircraft are dramatically more environmentally-efficient than others. easyJet's mix of new aircraft with high seat densities and high load factors means a traditional airline emits 27% more CO2 per passenger kilometre than easyJet. Over the course of our last financial year, easyJet emitted 95.7g CO2 per passenger kilometre - which means an easyJet passenger's environmental footprint is less than the 104g CO2 per kilometre of the Toyota Prius.