Betcha never knew that, on average, it is more energy-efficient to fly across the U.S. than to drive alone. But don't rush to board a plan just yet: Pollution controls on planes sure aren't pretty things. For example, planes release hundreds of millions of gallons of smog-producing chemicals a year just landing and taking off. If you must travel, it'd be far better for the environment if you took a bus; buses are nearly six times more energy-efficient than planes. Unfortunately for the bus industry and the environment, however, U.S. air travel is expected to increase by 85 percent in the next 20 years. Read more fun facts about flying on the Grist Magazine website.