Understanding Probability Language
This section presents basic concepts associated with risk analysis and the language used by
the FAA to characterize the likelihood of an accident or incident. When taking the risk matrix
defined by the FAA for its internal SMS and to illustrate SMS guidance and advisory material
for Part 139 airports, likelihood definitions are presented in two forms: expected period for one
event to occur and expected number of departures to occur, as shown in Table H-1.