Secure Equity in Airline Transportation Act of 2017 or the SEAT Act of 2017 This bill directs the Department of Transportation to issue a final rule to revise a federal regulation relating to oversold flights to prohibit an air carrier from denying air transportation to a passenger on an oversold aircraft that the passenger has boarded based on the status of the passenger with respect to the carrier's priority rules and criteria for determining which passengers holding a confirmed reserved seat shall be denied boarding in the event that an insufficient number of volunteers come forward.