When the blueprint equals to the plane in weight, the plane can fly. (Many people fail to design a flyable plane because he/her gives up when his/her blueprint nearly equals to the plane in weight.

• 当设计图纸的重量等于飞机的重量时，飞机就能飞行了。（许多人设计的飞机没能起飞的原因是他（她）设计图纸的重量快要等于飞机的重量时，他（她）先飞了。）