The Environmental Protection Agency is establishing Federal drinking water requirements (known as national primary drinking water regulations or NPDWRs) for aircraft public water systems (hereafter, aircraft water systems) under the Safe Drinking Water Act (SDWA). Federal drinking water standards were primarily designed to regulate water quality in stationary public water systems, and the application of these requirements to mobile water systems with the capability of flying throughout the world has created implementation challenges. This final rule's requirements are intended to tailor existing health-based drinking water standards to the unique characteristics of aircraft water systems for the enhanced protection of public health against illnesses attributable to microbiological contamination. EPA believes that this approach will better protect public health while building upon existing aircraft operations and maintenance programs, better coordinate Federal programs that regulate aircraft water systems, and minimize disruptions of aircraft flight schedules.