This is English secondary school question as to Why was the writer happy when he decided to fly in the night?
The reason is pretty simple. As per the passage the writer was happy because he was going home where his family was and he would enjoy his holiday with family and friends.
So when you have a question
Why was the writer happy when he decided to fly in the night?
Quick answer : To enjoy holiday with family
Why was the pilot happy. Give two reasons?
1) He was flying at high altitude above and countryside was sleeping.
2) He was dreaming of his holiday with his family.