Decoy flares are customized materials, which are capable of yielding thermal signature to interfere with IR guided missile seekers. In this study, different decoy flares compositions based on Magnesium/Teflon/Viton (MTV) (with fuel percentage ranging from 40:70 wt %) were developed by granulation and subsequent pressing. The spectral performance of developed decoy flare formulations was measured to thermal signature of jet engine nozzle using (FT-MIR 2-6) spectrophotometer. The jet engine thermal signature was characterized with two characteristic peaks over α band (2-3μm) and β band (3-5μm); this signature was correlated to black body emission by the nozzle at 690 0C. Absorption of the IR emission by air could attenuate the signal over the band 3-4 μm due to CO2 and H2O IR absorption. The characteristic intensity ratio of jet engine nozzle (α/ β) = 0.26 . The developed decoy flares offered similar thermal signature but with higher intensity due to the formation carbon soot and MgF2 as black body and active IR emitter respectively. Quantification of these emitting species in the combustion flame was performed using the ICT thermodynamic code. MTV decoy flare with 65 wt % Mg offered an increase in the intensity of α band and β by 21 and 4 times respectively. This customized formulation offered the formation of MgF2 (molecular emitter) and C soot (grey emitter) at 42.4, and 8.8 wt % respectively. It is also offered 48 wt % Mg fuel which would be oxidized in the flame and add much more heat with the formation of MgO (grey body). The characteristic intensity ratio Ɵ was found to be 0.96. This is manuscript would open the route for the development of customized decoy flares with tailored spectral performance.