While you don't have to go so far as to fashion your own wings from chicken feathers and wax to fly carbon neutral (just ask Icarus how that worked out) have you ever wondered just how much fuel it takes to get a passenger plane off the ground and keep it in the air? Think about it this way: A plane and a car leave on a 60-hour cross-country car trip from San Francisco to New York. Who uses more fuel? The answer: While the car takes longer to get there, it burns up about the same amount of fuel per passenger,  as a five-hour cross-country flight. But in a plane you'll be spewing 5.59 tons of carbon dioxide -- more than twice the 2.2 tons you'd emit driving your sedan the same 7,500 miles.  

Americans spend way more time in their vehicles than they do in the mile high club. While air travel accounts for about 10 percent of all carbon emissions in the U.S., versus 36 percent for passenger cars almost eight times as many miles are traveled in cars than by plane. With such fewer trips, and shorter travel times how could planes account for such staggering amounts of greenhouse gases?

The biggest factor is the use of hydrocarbons. While technologies like biofuels, efficiency standards and batteries can solve our emissions issues with cars, there are no alternatives for jet fuel. To make matters worse,gases released at altitudes where planes cruise have a much greater impact than those on the ground due to something called the radiative forcing effect. In all, the damage is about 2 times that of driving a fuel-efficient car.

Luckily there are peole out there doing their best to combat this issue. Organizations like TerraPass and TreeFlights allow you to purchase carbon offsets that go towards wind and solar energy development or planting trees in the rainforest. Also, in 2007 Delta Airlines became the first to offer their passengers the opportunity to purchase carbon offsets with each ticket purchase. Other airliners such as Jet Blue and Virgin Airlines allow you to fly almost carbon neutral.