Unmanned aerial vehicle (UAV) as an aerial base station is a predominant cost-effective solution of coverage extension in wireless communication network. It has a potential to provide disaster relief solutions and public safety services by enabling low power, highly reliable, and low latency connectivity. In this paper, deployment of UAVs in a given geographical area with coverage extension capacity is analyzed at low altitude platform. This model includes UAV with downlink users and Device-to-Device (D2D) communication underlaid with cellular network. In this work, analysis is given for dual (two) UAVs by considering two scenarios: with interference and without interference. Coverage probability and system sum rate are derived, which depends on the UAV altitude and D2D density. Our analytical results show that significant improvement in terms of coverage probability and system throughput is obtained as compared to single UAV case.