Management of flight operations in or near volcanic ash

Description
The abrasiveness of volcanic ash affects the operation of aircraft, causing engine malfunction /failure. Encounters with volcanic ash lead to reduced or complete loss of thrust and failures of electrical, pneumatic and hydraulic systems.
EASA - Flight in Airspace with Contamination of Volcanic Ash
ICAO - Manual on volcanic ash, radioactive material and toxic chemical clouds
ICAO - Handbook on the international airways volcano watch/ Operational procedu…
The Weekly Volcanic Activity Report 
ICAO - Risk management of flight operations with known or forecast volcanic ash…
Guidance regarding flight operations in the vicinity of volcanic ash
UK MET Office - Quantitative Volcanic Ash (QVA) Forecasts
IATA - Global Tactical Operations Portal
ICAO - Volcanic Ash Contingency Plan