A heavy airplane may not be able to fly. Sometimes, the airplane will carry less people or less things so that it weighs less. Then, it can fly and fly far.

The fuel (gas) airplanes use weighs a lot. Planes also carry people and their bags. They also carry other things like mail or things in boxes.

Because of all this weight engineers make parts that will not break. They also make the airplane strong so that if a part breaks the plane will not fall apart. If a strong wind hits the airplane it will not crash.