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 pilots
- F. travelling by air was very cheap
填空题
Air transport companies use different planes 1.
填空题
The United States was the country where 1.
填空题
The forty years from the 1930s to the 1970s was an important period 1.
填空题
Nowadays airports provide all kinds of services 1.