When the plane flies very high.这个动词对吗?为什么?

问题描述:

When the plane flies very high.这个动词对吗?为什么?
When the plane flies very high ,Henry can stand up and walk around .He can also read books ,newspapers or see films .The air hostess will bring him food and drink.Henry can enjoy the flight and arrive home soon.

应该对.但是还要看语境才知道这里用一般现在时对不对.