The FAA requires a full scale demonstration of the emergency plan every three years of those airports certified under 14 CFR part 139. This excerpt of FAA Advisory Circular 150/5200-31A (e) states:
Full Scale Exercise - The full scale exercise is the most comprehensive test and is intended to evaluate the operation capability of the emergency management system in a stress environment with actual mobilization and response capability. It uses all the resources and requires reaction from equipment and personnel that would normally be available if the exercise were an actual emergency. The FAA requires a full scale demonstration of the emergency plan every three years of those airports certified under 14 CFR part 139.
The full scale demonstration requires a simulated emergency, as it would in an actual aircraft disaster, for full certificated airports commensurate with the index of the airport, to ensure that all personnel having duties and responsibilities under the plan are familiar with assignments and are properly trained.