Is it possible to fly? Many times I see myself flying/floating in dreams. Not so high, but 1-2 feet above the surface. I make a second step upwards before my first step touches the surface/while my first step also holds up in air. Last night i was asked by myself (in the dream) how I am doing this. I don't know why but i replied 'its all about breath control'.
Whenever this flying happens in dreams, it leaves behind an amazing experience. I recall everything of those scenes. Whenever I breath-in, I raise up in parts and whenever I breath-out or lose control, I touch back the floor.
Almost 1 year back I had watched a programme on discovery channel which was about a monk who can fly/stay uplifted.
I wish to know, 'is it possible to actually fly? If yes, then how? If yes, then why one should do this 'as per buddha?
This is actually nothing special to feel excited about. In Ayurvedic terms, when Vatha(air element) is imbalanced in the body, people tend to see dreams of flying. More information here

On the other hand, the ability to fly through the air is just one of the many psychic feats an advanced meditator can perform. It has nothing to do with dreaming. It requires great dedication in the practice of Samatha meditation. Visuddhimagga explains how it can be achieved based on the 4th Jhana.


  If yes then why one should do this?


It's the same reason why one gets into an airplane. To travel longer distances easily. According to the stories, in the past, monks with psychic powers have used this method to travel when they don't have a specific destination in mind. ex: when going on alms round. 
But if they want to go to a specific place, they would simply disappear from where they are and appear in the destination. 
Lord Buddha himself has said to have used this method when he visited Sri Lanka 3 times.