Modeling infrared sensors, such as Infrared Linescanners and FLIRs, is important to air-borne reconnaissance, because it allows predic-tion of sensor performance during actual use. To date, considerable effort has been expended on modeling FLIR performance so as to include the CRT display and the observer in a real-time environment. Less effort has been directed toward modeling infrared linescanners in real-time situations where a CRT is used for onboard display. The traditional sensor figures of merit, such as MTF, NET, MRT and MRTD, are re-viewed as well as some of the most useful com-putational programs, such as the NV&EOL Static Performance Model (Ratches Model). These programs must be slightly modified to adapt them to the prediction of infrared line-scanner performance in real-time reconnaissance, and some simple adaptations are noted. Efforts to extend the modeling to predict performance when an automatic target screener is inserted between the sensor and the display or between the sensor and observer are briefly noted.