一、引言海阔凭鱼跃，天高任鸟飞，一幅迷人的自然景观。然而事情总是相对的，鸟的自由多了，人的自由就少；有了鸟的随心所欲，航空活动就受到了限制。保护环境无疑是对的，但在某种意义上它也给人类自身带来某些麻烦，有的甚至是灾难。应当研究并创造一种两全其美的方法，既 First, the foreword The vast sea diving, sky-high bird flying, a charming natural landscape. However, things are always relative. There is more freedom for birds and fewer human freedoms. With the freedom of birds, aviation activities are limited. It is undoubtedly right to protect the environment, but in a certain sense it also brings some troubles for human beings themselves, some even disaster. We should study and create a method that gives the best of both worlds