This work focuses on the determination of optimum operational jet-to-jet spacing of inline jet impingement heat transfer. Air jet impingement apparatus was used for the exercise. Arrays with the same jet diameter of 0.3mm but of jet-to-jet spacings of 0.9mm, 1mm, 1.2mm, 1.3mm, 1.4mm, 1.6mm, 2mm, 2.2mm, 2.5mm and 3.8mm were tested at flow rates of 1.67x10-5m3/s, 3.33x10-5m3/s, 5x10-5m3/s, 6.66x10-5m3/s, 8.3x10-5m3/s, 1x10-4m3/s, 1.17x10-4m3/s and 1.33x10-4m3/s. Each array was tested by hanging it on the aluminium holder of the experimental apparatus. The heating element of wattage capacity 1000Wwas connected to the power source. The heater was switched on to heat the bottom side of the copper plate and the blower was turned on to impinge air on the smooth and flat target plate. Air was regulated to the desired flow rate using a gate valve. The jet temperature as well as the surface temperature were measured using an infrared thermometer at every flow rate tested. Result showed that the optimum jet-to jet spacing was found to be in the range 5d ≤ s ≤ 7d.