This research describes a new method to ensure the safety of sense and avoid (SAA) functions for unmanned aircraft systems (UAS) in the presence of multiple intruders. In this work, integrity and continuity are used as quantifiable safety performance metrics. Whereas previous research addressed a single intruder, the approach described in this paper can account for multiple intruders. Integrity and continuity are addressed though determination of the probability of data mis-associations for multiple intruders. A mis-association occurs when the system incorrectly associates one intruder's measurement with another intruder's trajectory. Incorrect intruder associations are hazardously misleading information impacting integrity. This impact on integrity has a second order effect on continuity. A sensitivity analysis is performed based on two two-intruder encounters. The resulting impact of mis-associations between multiple intruders on integrity and continuity is quantified for a nominal composite SAA sensor. The sensor characteristic trade space is explored. The concepts and methods in this research are intended to be used as a tool for certification authorities to set potential requirements for integration into the national airspace system.