Unmanned aerial vehicles (UAVs) which are commonly known as drones are highly reliable in data transportation, especially whenever terrestrial access is unavailable due to geographical limitations. Several UAVs might collaborate to perform tasks in several applications such as rescue, military, and others. This collection of UAVs is known as a swarm of unmanned aerial vehicles. Drones can be used as aerial relays in complex communication scenarios thus establishing a reliable end-to-end transmission. Wireless Sensor Network (WSN) consists of sensor nodes and base stations. The sensors of WSN are widely dispersed in predefined geographical fields. These sensors might be used for continuous monitoring for example temperature or might be used for event triggers example whenever the temperature exceeds a certain threshold an alarm is fired. In a crisis case scenario, the base station which acts as a relay to upload the sensed data to the internet might be nonfunctional thus resulting in a disconnected network and loss of sensed data. This paper proposes the usage of a swarm of UAVs to upload data from the WSN network to the internet whenever the base station is nonfunctional. This paper will study the mathematical correlation between the parameters of this network taking into consideration the constraint to avoid collisions between the UAVs. A simulation using MATLAB studies the effect of the number of levels in the WSN, the range of communication, UAV's velocity, and UAv's trajectory on the network performance.