So according to Reuters, Batman could actually fly, this is according to some a group of British physics. 

In a paper titled "Trajectory of a falling Batman", the group argued that if he jumped from a 492-foot high building, the 15-foot wingspan of Batman's cape would allow him to glide 1148 feet. However, he would reach a speed of 68 miles per hour before hitting the ground at a life-threatening speed of 50 mph.

So According to this paper for Batman to actually fly, he would need: 

A bigger cape

He could opt for using active propulsion, such as jets to keep himself aloft

Actually be a real person! (I added this one)