This document addresses the topic of GNSS Reversion/Contingency in the context of PBN operations. The main emphasis is placed on terminal and extended terminal operations in a surveillance environment. Operations in a non- ATS surveillance environment as well those in the Final Approach are also covered for completeness. This document is not intended to be a definitive guide to contingency operations for PBN. Rather, its explanatory nature and use of sample scenarios are provided as a ‘starter pack for ANSPs and regulators to assist in their deliberations when planning contingency operations for GNSS reversion. It serves as a bridge document between existing EUROCONTROL guidance material already published to support Airspace Planners and Infrastructure Planners implementing PBN. This document is deliberately not detailed: it seeks rather to enhance understanding on the shared challenge of providing for GNSS contingency/reversion.