Quantitative aspects of infrared thermographic detection of water in aviation honeycomb panels are discussed in the framework of both 1D analytical and 3D numerical models. A criterion for the transition from 3D to 1D test geometry is introduced, and the influence of the honeycomb cell structure on the modeling results is demonstrated. Optimal test conditions are formulated both theoretically and experimentally in two practical cases where the force of gravity causes the water to be against the facesheet at the bottom of the cells or where a water gap separates the water from the top facesheet.