Level B1 Making Question with the 是……的 Sentence Structure

A warm reminder: click the video in this post, you will see the pinyin and hear my reading of the example sentences.
If you are not familiar with the 是……的 sentence structure yet, maybe it will be better to read  Level B1 Sentence Structure 是…… 的 first before you start to read this post.

In this post, we will continue to talk about the 是…… 的 sentence structure. Specifically we are going to make questions based on the original declarative sentence examples mentioned in the post Level B1 Sentence Structure 是…… 的

He went to Xi'an yesterday.
他昨天去了西安。

To emphasize that he went to Xi'an yesterday, not another day.
他是昨天去西安的。
If we have question about what time he went to Xi'an, we may ask, "When did he go to Xi'an? " 

他是哪天去西安的？ ( The only thing we need to do is replace the time part with the question word 哪天 (which day, when)）

Sometime, we can omit 是 in above question, then we get:

他哪天去西安的？

(Notice that here we can not drop the 的 at the end of the question. If so, then meaning of 他哪天去西安？will be "When will he go to Xi'an?" )

He went to Xi'an by plane yesterday.
他昨天坐飞机去了西安。

To emphasize the time part:
他是昨天坐飞机去西安的。

To ask about the time information:

他是哪天坐飞机去西安的?

To clarify that he took plane, not train or bus.
他昨天是坐飞机去西安的。
To ask about the way of transportation he used to go to Xi'an yesterday:
他昨天是怎么去西安的？    （Now we just replace the transportation way 坐飞机 (by plane) with 怎么 (how, in what way or method))

He went to Xi'an by plane yesterday to visit a friend.
他昨天坐飞机去了西安去见一个朋友。

To clarify the time:
他是昨天坐飞机去西安去见一个朋友的。
To ask about the time information:

他是哪天坐飞机去西安去见一个朋友的?

To emphasize the way of transportation:
他昨天是坐飞机去西安去见一个朋友的。
To ask about the way of transportation he used to go to Xi'an yesterday:
他昨天是怎么去西安去见一个朋友的?
Or we can make the question simpler by drop some information that is not really necessary ( in this situation,去见一个朋友, to visit a friend, is not really necessary)  in our question:

他昨天是怎么去西安的?

To emphasize the purpose:
他昨天坐飞机去西安是去见一个朋友的。
To ask about the purpose or reason why he went to Xi'an
他昨天坐飞机去西安是为什么？  （ Here we replace the purpose 去见一个朋友, to visit a friend, with the question word 为什么(why, for what reason) . Also please notice that we drop the 的 at the end of the sentence, otherwise it will sound awkward. )

Or we can ask this question without the 是……的 structure:

为什么他昨天坐飞机去西安？   

or 

为什么他昨天去西安？

But there is a little difference between the two ways to ask question. With 是……的 structure, we show more curiosity about the reason.

Related posts:
Making Negative Sentence with 是……的 Structure
Level B1 Sentence Structure 是…… 的