Jet flight is getting greener, but what the airlines don’t want to talk about is that you will pay for it with your kneecaps.

Airbus chief operating officer John Leahy says “the more you divide the fuel consumption through more seats and higher load factors the lower the carbon footprint per person.”

Leahy says some of the customers for its 500 seat category A380 aren’t interested in its spacious economy seating but want to put in “torture tubes” (our words) the same size as those in current jets.

This means that the newest and largest jet ever built will give a fuel economy of 1.9L/100 kilometres or less carrying passenger loads of up to 800 compared to a test flight audited 2.9L/100 kilometres carrying 525 seats which include the heavyweight trappings of luxury premium cabin appointments.

One can even argue it has always been the Airbus agenda to segue ‘Jetzilla’ — as some call the A380 — into a marketing weapon of mass discomfort at unbeatable prices.

The wing and substructure of the beast are built not for the requirements of the initial model that starts flying with Singapore Airlines this year and Qantas and Emirates next year but for the ‘stretched’ versions in four or five years’ time, that could shift well over 1,000 passengers per flight.

But for the present, the fuel burn of the initial A380 compares to somewhere between 13L/100 kilometres and 16L/100 kilometres for a well maintained four or five seat family sedan in country freeway conditions, and compares ever better when only the driver is being carried, or the road is congested.

It’s the same story for the much smaller but hi-tech Boeing 787 which starts its test flight program later this year for service with Jetstar next year.

Boeing originally offered lots of passenger space. But the airlines said ‘stuff them in’, making the so-called 787 Dreamliner as much an ordeal as a high density A380 or the packed little shockers that most airlines now operate on typical intercity services.

Not nice, but very cheap, and green.

The official FAA figures for the US show that in 2006 it carried 12% more passengers and 22% more freight than 2000 but used five percent less fuel and emitted 10 million tons less of CO2 in the same time.

The results are mostly due to cramming them in, not using new jets. The US carriers are in such poor fiscal shape they can’t invest as widely in new technology fleets as Asia-Pacific, Middle East and European carriers.

But they also show that people can fly more yet reduce the individual and aggregate carbon footprint of air transport.