I am sure you are preparing for an interview for an Air hostess. Actually this is the most common question that is asked at such interviews for selection of Air hostess in an airline.
The best answer for this question should be something like " I want to join Airline as an Air hostess because of many reasons. First of all it is my passion. I wanted to be an Air hostess since childhood. So being an air hostess would make my dream come true. Secondly, I have a passion for hospitality. And thirdly, I know what it takes to be an air hostess and I believe I have all those qualities of commitment, hard work, patience, cheerful etc. So that is why I want to join airline as an air hostess."