The purpose of this Guidebook is to provide an updated and focused overview regarding the planning and design of airport terminal buildings in the United States. This Guidebook's intended audience includes airport managers and their staff, airport planners, architects, and the aviation industry-at-large. This Guidebook is intended to supplement the guidebooks provided by the International Air Transport Association (IATA) and the Federal Aviation Administration (FAA) with updated information and a fresh outlook for terminal planners and designers. This Guidebook represents a snapshot in time within a continuously evolving set of industry planning principles and regulations. As such, the reader must remain vigilant to possible updates and changes to the contents of this document. This Guidebook attempts to provide a thorough understanding of all the issues to consider when undertaking the planning and design of terminal facilities in an ever-evolving commercial aviation market. To plan and/or design an airport passenger terminal appropriately, it is important that any future terminal facility is based on a sound quantitative program of functional requirements that are based on future forecasts of air passenger and aircraft activity. For this reason this Guidebook also includes the results of Airport Cooperative Research Program (ACRP) Project 07-04, "Spreadsheet Models for Terminal Planning and Design." Additionally, this Guidebook makes reference to other ACRP projects that have relevance to the planning and design of airport passenger terminals.