Progress the story until you get to Wonder Tower. Go to the large ledge just before you grapnel up to the maintenance hatch and jump glide
Push forward (or backwards depending on your controls) on the left stick from the very beginning of the jump, so that way you are flying up. If you don't you will fall. There are times where the game makes you fly up, circle back to the left or right until you're facing the city again.
Video credit Rooster Teeth:
Another way could be use the Telephone pole (I think that what it is, I dunno) and power grapnle off of the pole to continue your flight.
Video Credit IGN: