Measurements of IR background variation or clutter are important for determining target detectability. Image sequences of widely varied ground-clutter types were recorded with the Airborne Infrared Imager (AIRI), housed in a wing pod of the Airborne Seeker Test Bed (ASTB) aircraft. Target detection statistics were derived for various backgrounds (ocean, ocean glints, desert, forest, shoreline, and urban). MWIR and LWIR images were processed to determine the minimum point-target contrast temperature detectable in various clutter types. This clutter metric was found to be relatively insensitive to changes in wave- length, season, or spatial scale, but to vary strongly with clutter type. These statistics are used to predict clutter- limited detection ranges for generalized targets in appropriate scenarios. Reduction in detection range from most benign clutter (ocean) to most severe clutter (urban) was found to be 7-9 dB, depending on waveband.