Air leakage is an important consideration in all construction. Tighter buildings are more energy efficient and comfortable. Although large buildings are rarely blower door tested, architects, enclosure consultants, manufacturers, and installers spend time and money to provide air tight buildings. Details within the contract documents and subsequent shop drawings indicate the intended location of the air barrier. However, over the course of mockup construction, mockup testing, and project construction, air leakage issues often arise that were not addressed prior, generally at unusual conditions and transitions. These locations can be difficult to detail and are typically overlooked. This presentation will first review the basics of air leakage detailing, and then provide specific examples where project documentation did not address air leakage sites, which were found in the field. Implemented field fixes will also be presented. Although project-specific, these case studies will demonstrate typical locations that must be carefully vetted during detailing.