The use of Unmanned Aerial Systems (UASs) is expanding speedily. This results in a need to integrate UAS traffic into non-segregated airspace. However, this integration introduces a risk of a mid-air collision between a UAS and a manned aircraft in the airspace. To deal with this issue, we present a UAS traffic simulation model (or UAS model) to assess the risk of a near mid-air collision (NMAC) between a UAS and another manned aircraft operating in Canada's Northern airspace. In this thesis, we present two implementations of the UAS model. The first implementation is a proof-of-concept model which involved the Cell-DEVS formalism and software, while the second implementation is a more complete model implemented with the Processing software. Our results show that there is a low probability of an NMAC occurring between a UAS and an aircraft in the airspace region being considered in this work.