Book excerpt: This conference was prompted by the occurrence of 5 encounters between passenger jetliners with drifting clouds of volcanic ash from the 1989-90 eruptions of Redoubt Volcano in Alaska. Examines 5 principal areas, including: how volcanoes produce ash clouds, the damage and impacts resulting from ash-cloud encounters, communications procedures for mitigating the risks from volcanic ash, the meteorology and modeling of ash-cloud movement, and methods for detection and tracking of ash clouds. 60 technical presentations are included.