“蜀道之难,难于上青天”。这是李白反复(讠永)叹的千古名句。人们常把极为困难的事情同登天之难相比拟,可见“上青天”乃是难中之最难者。尽管人们深知其难,但世代以来,人类始终憧憬着有朝一日到蓝天中自由飞翔。自从1903年12月17日莱特兄弟首次架机飞行成功以后,登天的困难被攻克了,美好的理想渐渐实现了。今天,最快的喷气式客机的速度已超过两倍音速。依这个标准看来,莱特兄弟的纪录的确是微不足道的:他们飞得最远的一次,只达到284米,却费了将近一分钟的时间。虽然这有史以来的第一架飞机,粗陋得象一只丑小鸭,然而正是以它为开端,航空事业才蓬勃发展起来。飞机很快又被用于战争。仅十年后,至第一次世界大战爆发(1914年)时,轰炸机时速已达130公里,侦察机则达220公里。三十年后, “It’s hard to marry, it’s hard to go to heaven.” This is Li Bai’s repeated (Yong Yong) sigh of the ages. People often compare extremely difficult things with the difficulty of ascending the heavens. It can be seen that it is the most difficult person in the world. Although people are aware of the difficulties, humans have been flying freely from day to day in the blue sky. Since the first flight of the Wright brothers on December 17, 1903, the difficulty of climbing the sky has been overcome, and a beautiful dream has gradually come true. Today, the fastest jetliner has more than twice the speed of sound. According to this standard, the records of the Wright brothers are indeed insignificant: they flew the furthest time, only reached 284 meters, but spent nearly a minute. Although this is the first aircraft ever built, it looks like an ugly duckling. However, it is only with this that the aviation industry has flourished. The plane was soon used again for war. Only ten years later, at the time of the outbreak of the First World War (1914), the speed of bombers reached 130 kilometers per hour and the reconnaissance plane reached 220 kilometers. Thirty years later,