A lightning flash is composed of various energetic discharges called return-strokes which are believed to be responsible for the natural formation NOX in the atmosphere. We report the first experimental attempt in the simulation of such a process. The temporal evolution of electric breakdown in air at atmospheric pressure of two synchronized Nd:YAG nanosecond laser pulses was studied to understand the physical behavior of a double return-stroke lightning flash by shadowgraphy and interferometry techniques. The temperature of the second return-stroke reaches about 20,000 K after 1 ¿s of laser ignition of the second pulse and cools off more rapidly than the first discharge. The cooling rate of the heated gas is about a factor of two faster for the second simulated return-stroke. The estimated production of nitric oxide of two synchronized laser induced plasmas seems to be not substantially modified as compared with the sum of the isolated single pulses.