​​ICAO Annex 11 — Air Traffic Services, states (in section 2.31 - Contingency arrangements) that air traffic services authorities shall develop and promulgate contingency plans for implementation in the event of disruption, or potential disruption, of air traffic services and related supporting services in the airspace for which they are responsible for the provision of such services. Such contingency plans shall be developed with the assistance of ICAO as necessary, in close coordination with the air traffic services authorities responsible for the provision of services in adjacent portions of airspace and with airspace users concerned.

As part of offering assistance, ICAO has developed this Traffic Flow App, which provides an indicative estimation of the effect on traffic flows when an FIR is closed – both graphically, and in the form of a percentage increase/decrease graph.

This information can then be used as a basis for close coordination with ANSPs responsible for adjacent airspace, during the development if the contingency plan.

Further guidance material relating to the development, promulgation and implementation of contingency plans is contained in Attachment C to Annex 11.​​​​