Flock is revolutionising the way Drones fly in cities. It is a software that uses big data based algorithms to fly Drones. Our algorithms are able to drive the drones in a pro-social way, reducing the accident risk and nuisance they could have on the citizens. We use different real-time geo-data sources to calculate and predict the possible impact and nuisance drones can have on citizens and propose routes and flightpaths that reduce them. When drones are flown by an operators, Flock helps them plan flights in a safe way reducing the risk of accident and disturbance.