The use of unmanned aerial systems (UAS) by the fire service is becoming more common, especially for large outdoor fires where it is difficult to understand the state of the fire conditions or efficiently suppress the fire. The focus of this paper is to discuss the challenges that are currently faced in using UAS, which are limiting the broader application of these systems for use in large outdoor fire events. The paper provides an overview of UAS currently used today as well as some guides and standards that have been developed to support the use of UAS. Challenges for use of these systems are discussed based on technical hardware/software as well as operational details related to policy and training. These challenges highlight hurdles that need to be overcome by the community to support broader, more frequent use of UAS in the field.