Weight

Weight is the easiest force to understand. It's simply the weight of the aeroplane, caused by gravity that pulls it down towards the Earth. Although it's easy to understand, it is the force that makes it hardest for planes to fly. Jumbo jets, the biggest passenger plane in the world, can weigh as much as 450 tonnes! That's a lot of weight to lift into the air. So how do planes get off the ground? How does lift work?