晴朗的夜空中，仰望天空的时候，有时能看见一些红色、绿色和白色的闪光。伴随这些闪光的还有一阵轰隆隆的声音。这是飞机在夜空中飞行。那些红色、绿色和白色的灯是飞机上所装的导航灯，看起来就像红绿灯一样。不过，飞机上装这些灯可不光是为了让地面上的人能看见它哦！这些灯对飞行安全可是有大作用的。

Look up into a clear night sky and you may see some small green and white lights flashing slowly followed by a burst of sound. This is an aircraft flying above you. Although the sky is very big, when an aircraft is flying it is going so fast that it is easy for it to get into an accident with another plane. To avoid this, the pilot must always be aware of the space around the plane to make sure there are no other planes nearby. The green and white "traffic" lights you see on the aircraft are navigation lights, to help other pilots see the plane. The light on the left wing is red, the light on the right wing is green, and a bright, white light sits on the tail. When an aircraft is flying in the evening, it must use its navigation lights. If a pilot can see another plane's navigation lights, he or she can tell what direction the other aircraft is going in, and whether or not they need to change course. If the pilot sees all three lights, it means the other aircraft is in front heading away from the plane, and there is no danger of collision. If the pilot can only see a red or a green light, it means the other aircraft is crossing his field of vision, and they will not collide. If the pilot can see both the red and green light only, it means the other aircraft is heading towards him or her, and the pilot needs to take action to avoid a crash. During foggy weather, navigation lights alone are not enough, and the pilot must also rely on aircraft radar to determine the direction and distance of the aircraft. According to the radar's continuous use of radio waves the pilot can adjust the plane's flight path to avoid collision.

（北京林业大学通讯员黄典钰供稿 英语点津 Annabel 编辑）