Emerging Transportation Security Threats Act of 2019 This bill directs the Transportation Security Administration (TSA) to establish a task force to conduct an analysis of emerging and potential future threats to transportation security, including threats posed by the release of chemical or biological agents in aviation or surface transportation systems. The TSA must develop a threat mitigation strategy for each of the threats the task force examines in its analysis. The Government Accountability Office must conduct a review of the feasibility, risks, costs, and potential threat mitigation benefits of the TSA deploying its passenger and property screening assets to conduct screening in areas or facilities prior to passenger arrivals at airport terminals.