Before the first non-stop flight made in 1949, it______necessary for all planes to land for refueling.

Refueling a fuel cell car is more complex and dangerous than with traditional gasoline vehicles.

Before the first nonstop flight made in 1949, it_______ necessary for all planes to land for refueling.

Aerial _____ is the process of transferring aviation fuel from one military aircraft (the tanker) to another (the receiver) during flight. A: dumping B: fueling C: storing D: refueling

案例分析题 Scientists think that in the future space stations can be built for the following purposes EXCEPT ______. A: carrying passengers to planets B: acting as stop- over points C: refueling spacecraft D: providing supply of air, food and water

A helicopter making a round trip from a helideck with refueling capabilities to an unmanned platform will take 45 minutes each way. The helicopter should be carrying enough fuel to last（）. A: 45 minutes B: 1 hour and 15 minutes C: 1 hour and 30 minutes D: 2 hour