电子课本网 第139页

第139页

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       The first plane flew for the first time in 1903. In the 1910s, people used many planes in wars. Some 
planes could fly as high as 7,000 metres. In the 1980s, some planes could fly three times faster than the 
sound. Now, the largest plane can carry more than 800 people and keep flying for many hours. Every day,
about 5 million people travel by plane.