clear the mountain meaning in English

飞跃山峰

Byrd at once ordered his men to throw out two heavy food sacks . the plane was then able to rise and it cleared the mountains by 400 feet .
比拉德立刻命令随行的人掷下两个沉重的食品袋，这样，这架飞机才能升高，并在距山头四百英尺的高度飞越山顶。
The plane was then able to rise and it cleared the mountains by 400 feet
"这时飞机能上升了,并在距山头400英尺的高度飞越了山头。
The plane was then able to rise and it cleared the mountains by 400 feet
于是飞机可以上升了，它在离山头400英尺的高度飞越了过去。
The plane was then able to rise and it cleared the mountains by400 feet
这样，这架飞机才能升高，并在距山头四百英尺的高度飞越山顶。