详细解释:a. 轻于空气的
英语解释：
形容词 lighter-than-air:
relating to a balloon or other aircraft that flies because it weighs less than the air it displaces详细解释：
light.er-than-air
adj.（形容词）Having a weight less than that of the air displaced. Used of certain aircraft.轻于空气的：重量比周围的空气轻。用于某种航空器