Al-Hajj or pilgrimage is one of the biggest special events in the world; millions of pilgrims visit Mecca every year to perform the rituals of Hajj. The main challenge in this event is the huge number of pilgrims; therefore, terrestrial base stations overloading happen and it is not possible to provide a wireless coverage to all pilgrims. An innovative solution to manage this problem is to use Unmanned Aerial Vehicles (UAVs) as an aerial base stations to assist terrestrial cellular networks. In Al-Hajj, there are two types of users, indoor and outdoor users. In this paper, we propose using UAVs to provide wireless coverage for all users simultaneously in massively crowded events (such as pilgrimage). The existing Air to Ground and Outdoor-to-Indoor path loss models are utilized to study the problem of UAV placement with objective of minimizing the UAV transmit power. In order to find an efficient placement for UAV, we use Particle Swarm Optimization (PSO) and K-means with ternary search (KTS) algorithms. The simulation results show that the PSO algorithm provides better performance compared to KTS algorithm in finding the efficient UAV placement. More specifically, the employment of PSO algorithm requires less than transmit power by a factor of 5x compared to the KTS algorithm.