Flame propagation in a confined tube configuration was evaluated for aluminum (Al) and molybdenum trioxide (MoO3) thermites starting at room temperature and preheated up to 170°C. Flame propagation was analyzed via high speed imaging diagnostics and temperatures were monitored with thermocouples. Experiments were performed in an air-ambient reaction chamber at standard atmosphere pressure. Thermites were ignited using a Nichrome wire thermal ignition source. The flame propagation behavior for the nanocomposite thermite was compared to micron composite thermite of the same composition. Results indicate that increasing the initial temperature of the reactants results in dramatically increased flame speeds for nanocomposite thermite (i.e., from 630 to 1061 m/s for ambient and 105°C preheat temperature, respectively) and for micron composite thermite (i.e., from 251 to 544 m/s) samples. Experimental studies were extended giving a cooling time for the heated thermites prior to ignition and flame propagation. It is shown that when 105°C heated thermites are cooled; they propagate at the same rate as ambient temperature thermites. However, thermites cooled from 170°C demonstrate a reduction in propagation rate (around 21% for micron and 4% for nano composite thermites) compared to non-preheated case.