Only if speed actually pays off. With fuel as expensive as it is (and if it's too cheap, just tax it some more), that won't necessarily be the case. And if it i

Only if speed actually pays off. With fuel as expensive as it is (and if it's too cheap, just tax it some more), that won't necessarily be the case. And if it is, then getting people to fly less on economy flights is a better and economically more efficient way to reduce fuel consumption. Set an environmental goal and let the market sort out the process. Don't regulate the process itself.