Bill was a very good pilot. He had been in the air force for several years, and had been very successful. Now he was sent to a small field in the middle of a forest, from which aeroplanes were able to attack the enemy very easily, because it was near the front line, but difficult to find. The forest trees were very tall and very close on all sides, so planes had to dive down very steeply and then stop their dive very suddenly before they hit the ground. Only the best pilots were able to land safely, and even some of those lost their planes and were killed because they hit the trees or the ground.
After Bill had arrived, he was not satisfied until he was able to fly closer to the trees than any of the other pilots, and soon all the pilots who used that field were trying to beat each other at flying low over the forest. Every time that one of their aeroplanes came back from an attack on the enemy, the other pilots used to run outside and watch, to see how near the trees its pilot took it. If he succeeded in taking it very near, they laughed and shouted and bought him pints of beer at the bar when he got in.
Bill soon learnt exactly how near he was able to go safely, and then one day he flew so close to the tops of the trees that some of the branches scratched the bottom of his plane. The other men in the plane seemed rather frightened, but Bill only laughed as he landed the plane without any trouble in the middle of the field, while the other pilots on the ground shouted happily. 'How silly I am!' he said, 'I forgot that the trees have grown since yesterday!'