判断题 Some entrepreneurs, though they did not have much money, were able to provide passenger services because they had experienced pilots and surplus aircraft.

判断题 Radar technology was applied in the civil aviation system to track, identify and direct aircraft after WWII.

判断题 At the early stage of civil aviation, flight remained uncomfortable, expensive and unreliable, but it soon proved to be profitable.

判断题 Conditions on the first daily international scheduled flight were so spartan that passengers in enclosed cabins had to wear protective clothing against the freezing cold.

判断题 The first man-carrying lighter-than-air flying machine was used in war only.

判断题 Both Roger Bacon and Leonardo da Vinci believed that humans could fly by the flapping of wings.

判断题 DH-4 aircraft were equipped with fixed, synchronized, forward-firing machine guns by Fokker.

判断题 The first military aircraft was purchased by the US Army Signal Corps from the Wright brothers.