Airplanes pump 620 million tons of carbon dioxide into the air, accounting for 2 percent of total emissions.

Now, there are efforts to shake up the numbers.

Companies have agreed to cut emissions in half by 2050.  New technology that includes lighter planes will help.
A new weed called jatropha has been used to power test flights in New Zealand.

Experts say emissions will rise for another 10 years before they start to level off.

Another step airlines need to take is better air traffic management.  Industry experts say governments need to redraw their airspace to allow planes to have shorter flights.