It was late at night. The plane flew through the air. It flew through the air very fast. It flew through the air at 500 miles per hour. Five hundred miles per hour is very fast. A train does not go 500 miles per hour. A bus does not go 500 miles per hour. A ship does not go 500 miles per hour. Both the pilot（飞行员） and copilot（副驾驶员） were very sleepy（困的）. They both fell asleep. The plane flew past the city. Then the pilot and copilot woke up. They turned the plane around. They went back to the city. They landed at the airport. Their boss was angry. He asked, "Why is the plane late? Did you two fall asleep?" They both said, "Of course not, boss!"