Some 16,000 commercial aircrafts pump out 600 million tonnes of carbon dioxide every year. It is estimated that by 2020 airplanes will be the single biggest contributor to global warming. It is expected to be bigger than all the other sources of carbon emissions combined. Ground level emissions are less harmful than the carbon emissions by airplanes, for the simple reason that they are deposited directly into the atmosphere.

The emissions from a single transatlantic flight is double than that coming from an average car in the US for a whole year!

Burning aircraft fuel has a "radiative forcing ratio" of around 2.7; which means that the total warming effect of aircraft emissions is 2.7 times as great as the effect of the carbon dioxide alone. Also the contrails i.e. the artificial circus clouds made by the exhaust of aircraft engines; produce water vapour that forms ice crystals in the upper troposphere that trap's the earth's heat.