The infrared lock-on range of target aircraft plays a critical role in determining of aircraft survivability. Infrared emissions from aircraft are used for search, detection and tracking of the aircraft. Therefore, to reduce aircraft IR signature is essential to counter this threat, and are an important aspect of aircraft stealth technology.In this investigation, the effects of various engine nozzle configurations on the aircraft lock-on range were analyzed. A virtual subsonic aircraft was first selected based on the mission and engine performance analysis and then convergent-type nozzles were designed. After thermal flow field and nozzle surface temperature distribution were determined by a CFD code, IR signature analysis was conducted. Further, atmospheric transmissivity for various latitude and seasons was calculated using the well-known LOWTRAN code. Finally, assuming given IR guided missile sensor’s threshold, the lock-on and lethal envelopes were calculated for different nozzle configurations.