The McKinley Climatic Laboratory is engaged in a major upgrade to provide an improved capability for simulating large scale ground fog icing conditions for aircraft. The new capability will also provide an ability to simulate low speed in-flight icing conditions. This paper provides a description of the McKinley Climatic Laboratory’s Main Chamber, the world’s largest environmental testing chamber. The discussion emphasizes the equipment and techniques used to produce simulations of very large ground fog icing clouds for testing of both commercial and military full-scale aircraft. A discussion of other facilities that simulate icing clouds for aircraft applications outlines the primary advantages and disadvantages of those facilities to illustrate the current need for an additional large icing cloud simulation facility. An overview of the current project underway at the McKinley Climatic Laboratory to greatly improve the existing ground fog icing capability and extend the icing capability into the in-flight icing regime is presented. This New Icing Capability Project intends to create one of the largest artificially created icing clouds in the world which has the ability to simulate all icing cloud conditions identified in 14 CFR Part 25 Appendix C (FAA requirements for aircraft icing certification).