新概念英语mp3听力下载第二册lesson 79

First listen and then answer the question.
Why did the plane turn back?

    I used to travel by air a great deal when I was a boy. My parents used to live in South America and I used to fly there from Europe in the holidays. A flight attendant would take charge of me and I never had an unpleasant experience. I am used to traveling by air and only on one occasion have I ever felt frightened. After taking off, we were flying low over the city and slowly gaining height, when the plane suddenly turned round and flew back to the airport. While we were waiting to land, a flight attendant told us to keep calm and to get off the plane quietly as soon as it had touched down. Everybody on board was worried and we were curious to find out what had happened. Later we learnt that there was a very important person on board. The police had been told that a bomb had been planted on the plane. After we had landed, the plane was searched thoroughly. Fortunately, nothing was found and five hours later we were able to take off again.