'Emergency' phase or modes are those situations following unforeseen or sudden catastrophic events that may lead to potentially unsafe situations and/or partial or full interruption of the air navigation services (ANS) provision, therefore prompting an immediate response to contain the adverse impact and, where feasible, initiate recovery actions.
It is recognised, however, that not all situations can be foreseen. In addition, no two situations will be the same and so no emergency or service continuity plan can cater for every eventuality. That said, ANSPs must be prepared for certain common factors. For example, they must be able to deal with unexpected events and it is the ability to respond to these in a safe, orderly manner which provides the overriding rationale for the development of contingency plans. Safety is, and must remain, the number one priority. A system (technical, people and procedures) working in 'Normal' operation can evolve directly into an “emergency” situation; or a system can deteriorate into a “degraded mode of operation” that further evolves into an “emergency” situation.
For 'emergency', 'degraded' modes of operation and ' service continuity', it is important to conduct both a safety assessment and a security risk assessment. The aim is to ensure that the planned contingency measures meet safety and security requirements set at the policy step.