Speed vs. distance

Planes require an INCREDIBLE amount of force to stay in the air, and to go faster they have to burn a lot more fuel. The physics equation that explains this is a little complicated, but the main idea is that in an energy equation, velocity is squared: so it takes 4 times the amount of energy to go twice as fast. We can also see this idea in braking distance, although other factors keep it from being mathematically perfect:

Notice the jump from 30mph to 60mph - twice the speed, more than 3 times the stopping distance

This is one of the main reasons that speeding is so dangerous: not only would a crash be more intense, but avoiding one gets exponentially harder. Check out this article about some of the fastest things ever.

The trade-off for speed, however, is longevity: this very slow solar plane is gearing up to fly all the way around the world off of ONLY solar power. It's already made a trip across the U.S. - but it took 4 days, while jet engines can do it in hours.  This plane can technically stay in the air for weeks at a time, but human pilots can't last that long - the plane stops so that the human energy can recharge, not the plane's :)

Don't fall sleep while you're driving, people!