## 4.3.5 Monitoring and Tracking of Changes Added to the Operating NAS 

A change is considered to be part of the operating NAS only after monitoring is completed, the safety performance target is achieved and maintained, and/or the predicted residual risk is verified. At that point, the NAS change is monitored through existing Safety Assurance processes to determine whether an acceptable level of safety is maintained. The NAS change and all of the associated safety requirements become part of the operating NAS, which will become the basis from which all future NAS changes will be measured. If a safety requirement is altered or removed from a NAS change that was made part of the operating NAS, a new SRM analysis must be performed. 

The documentation that was developed during the SRM process is critical to Safety Assurance functions, which often use SRM documents as inputs to assessments and evaluations. The process for preparing, performing, and documenting the safety analysis is described in Section 5. 

