This Advisory Circular (AC) provides guidance for reference material covering Aircraft Fire Extinguishing Agents. The Federal Aviation Administration (FAA) recommends the guidelines contained in this AC for Aircraft Fire Extinguishing Agents. This AC is not mandatory and does not constitute a regulation. However, the information it contains provides an acceptable methodology for complying with Title 14 of the Code of Federal Regulations (CFR), part 139, Certification of Airports (Part 139). In the event of a conflict, part 139 takes precedence over the other documents identified in this AC.