Mahan Air and Terrorism Prevention Act of 2017 This bill directs the Department of Homeland Security to submit an annual report to Congress through 2020 that includes: (1) a list of all airports at which aircraft owned or controlled by Mahan Air (a Tehran-based commercial airline under U.S. sanctions) have landed during the preceding two years; and (2) for each such airport, an assessment of whether such aircraft continue operations at that airport, an assessment of whether any of the landings were emergency landings, a determination of whether additional security measures should be imposed on flights to the United States that originate from that airport, and an explanation of the rationale for such determination.