點解飛机起飛後要飛到三四萬呎咁高?

氣流穩定d ( 平流層 )
同埋唔受天氣影響 ( 飛得高過雲 而天氣絕大部份係雲層下方)


圖片參考：http://hk.wrs.yahoo.com/_ylt=A8tU32v7DD1HpUYA.wS.ygt./SIG=12o98gera/EXP=1195269755/**http%3A//www.batkhela.com/wallpapers/9071/displaypics/pics/pic-529.jpg

Nah, because of less drag induced by air and jet engines are more effective in thin air.

the main reason is the low air density resulting in low drag. And the contemporory jet engines are designed to be more effective on low density of air.

你講兩個都岩
仲有氣流穩定d ( 平流層 )
同埋唔受天氣影響 ( 飛得高過雲 而天氣絕大部份係雲層下方)

我估第一係高過雲層,減少被雷擊嘅機會,第二係愈高,氣壓愈低會愈慳油