填空题
- A. in the development of air transportation
- B. the earliest passenger flights were successfully operated
- C. to make travel easy and pleasant for the passengers
- D. to provide different services
E the shortage of qualified pilotsF. travelling by air was very cheap
填空题
Air transport companies use different planes ______.
填空题
The United States was the country where ______.
填空题
The forty years from the 1930s to the 1970s was an important period ______.
填空题
Nowadays airports provide all kinds of services ______.