If you are afraid of poisonous spiders (有毒蜘蛛), this is logical. If you are afraid of all spiders, even harmless ones, this is a phobia because it is illogical. Some people have phobias about heights being shut up in a small or large open area. It’s not logical to be afraid of these things when there is no danger, but a phobia is not logical. Fear of flying is another phobia. We always hear about a plane crash, but we don’t hear about the millions of flights every year that are safe. Riding in a car is thirty times more dangerous than flying, but most of us are not afraid every time we get into a car. It is not logical to be afraid of flying, but research shows that about 12 percent of people have this fear. People with a phobia about flying are afraid for one or more reasons. They are afraid of heights. They avoid high places, and if they are in a high-rise building, they don’t look out the windows. They might be afraid of being in an enclosed place like an elevator or a tunnel on a highway. When they get on an airplane, they can’t get out until the end of the flight, and the flight might last several hours or even more. Maybe they are afraid of the crowds and all the noise and people rushing around at an airport. This especially bothers older people. Some people are afraid of the unknown. They don’t understand the technology of flying and can’t believe that a huge airplane can stay up in the air. Though some people are afraid of flying, for many people it’s not important because they don’t really need to fly.