Airplanes become more fuel efficient with every generation, and there are plenty of ways old planes can be spruced up. Winglets can be added on to the end of wing's, reducing drag and reducing fuel consumption by 6 percent.
Just about every airline has made its planes lighter through creative means, like installing carbon fiber seats, cutting back on magazines, buying lighter beverage carts and trashing in-flight phones.
When it comes to the best, Southwest is the world's most efficient airline, saving 274 pounds of CO2 per flight. Continental, Jet Blue and Virgin Atlantic are also good choices.