Securing and Revitalizing Aviation Act of 2018 or the SARA Act of 2018 This bill authorizes the National Transportation Safety Board, in the case of an application for the issuance of an airman certificate, to review a denial that may not be considered a final denial by the Federal Aviation Administration (FFA) when the FAA has twice reconsidered the application and sustained a previous denial of that application. An airman may voluntarily surrender an airman medical certificate for cancellation at any time, unless the certificate is subject to a FAA order at the time of the voluntary surrender. The FAA shall review the process of reserving aircraft registration numbers and enact appropriate changes to ensure the fair participation by the general public, including the implementation of readily available software to prevent any computer auto-fill systems from reserving aircraft registration numbers in bulk. Any person who holds a seaplane rating from the FAA and successfully completes a free online education course on aquatic invasive species mitigation that is acceptable to the Department of the Interior may hold themselves out to the public as qualified to inspect aircraft for aquatic invasive species and to take action to mitigate the spread of aquatic invasive species. The bill amends the FAA Extension, Safety, and Security Act of 2016 to modify FAA tower marking requirements. The bill limits civil liability for certain individuals designated as representatives of the FAA, except for intentional or fraudulent misconduct.