Meteorological Service of Canada, has been active since the

(AIRS) were organized to characterize icing environments associated with freezing drizzle; develop better techniques for forecasting such events; and develop our ability to remotely detect icing regions. These field projects, involving instrumented aircraft, were conducted out of Newfoundland (March, 1995) and Ontario (1996/97, 1997/98, and 1999/00). Newfoundland and the Great Lakes are the two regions in North America with the highest frequency of freezing precipitation at the surface. Freezing drizzle, or supercooled large drops (SLD), is considered to be a dangerous icing condition that is not covered by current aircraft certification procedures. The median liquid water contents measured in clouds in both regions were similar, while the droplet concentrations and the frequency of occurrence of mixed phase clouds tended to be higher in Ontario. In both Newfoundland and Ontario, conditions with SLD were often found outside the envelopes used to certify aircraft for in-flight icing. Approximately 80 % of the SLD environments were assessed to have formed through a non-classical formation mechanism. Forecasting icing conditions remains a challenge. Although new, more physically realistic, in-flight icing forecast schemes have been developed, verification of these forecasts, using the in situ aircraft data, shows that considerable improvement can still be made