I will= I am going to
fly to France= go to France by plane= go to France by air
看题目出的横线在哪里,可以有多种改法,下面为参考：
I will fly to France tomorrow.
=I am going to fly to France tomorrow.
= I will go to France by plane tomorrow.
=I will go to France by air tomorrow.
有些时候还可以是 I am flying to France tomorrow.