Due to a projected shift in the majority of the world’s population towards urban areas and the existing traffic congestion in today’s cities, the possibility of using the third dimension for transportation of people and goods is being increasingly explored. The resultant congestion from an estimated demand of unmanned and Urban Air Mobility flights(UAM) in urban airspace would warrant a centralized mitigation framework. Additionally, the multi-stakeholder nature of UAM calls for a traffic mitigation approach that addresses the major concerns of UAM - safety and environmental impact. In order to address this problem, an Air Traffic Flow Management (ATFM) framework that follows a multi-path approach has been developed as a Mixed Integer Linear Programming (MILP) model in this paper. Compared to flights that follow a single fixed path, this multi-path approach is seen to show a delay cost reduction of upto 96.3%. On incorporating an impact mitigation part to the original ATFM framework, it was seen that delay cost increased by 25% compared to the multi-path model. On the other hand, the impact of traffic densities in urban airspace was seen to reduce by 43.47%. This further leads to trade-off studies between delay cost and the impact of traffic densities in airspace.