填空题

Air Transportation
1 Airplanes are used to carry passengers, cargo and mail. Air transport companies operate scheduled airlines and non-scheduled services over local, regional, national, and international routes. The aircraft operated by these companies range from small single-engine planes to large multiengine jet transports.
2 The first air passenger services began in 1910, when dirigibles began operation between several German cities. The first scheduled airplane service to carry passengers began in the U. S. in 1914. Several experimental airmail flights took place in India. Europe, and the United States before World War Ⅰ, but air transport services did not become a true business until after the war.
3 During World War Two, intercontinental air transport became firmly established. After the war the new long-distance transports with advanced facilities were increasingly able to avoid storms and strong wind and make flights more economical and consistent. A new generation o "jumbo-jet" transports began operations in 1970, and the supersonic transport entered passenger service in 1976.
4 During the 1970s the number of domestic passengers on U. S. airlines increased about 78% , and during the 1980s the figure was up about 58%. In 1990 there were 41. 8 million international passengers, the figure was a 75% increase over 1980. The total cargo flown by U. S. airlines almost doubled during the 1980s, from 5. 7 billion to 10. 6 billion ton-miles in 1990.
5 Major airports provide a wide range of facilities for the convenience of millions of travellers. These range from such basic services as ticket-sales counters and restaurants to luxury hotels, shopping centres and play areas for children. International airports must also have customs areas and currency-exchange counters and so on.

• A．Airport services
• B．Training of pilots
• C．Beginning period
• D．Rapid growth in the U. S.
• E．Development
• F．Competition

Paragraph 4 ______.