A transient mathematical model was presented for a single pass flat plate solar air heater. This model was based on an analytical solution of the energy balance equations for various elements of the heater. The flowing air temperature was assumed to vary only in the flow direction. The thermal performance of the heater was investigated by computer simulation using the climatic conditions of Jeddah (lat. 21 degrees 42' N, long. 39 degrees 11' E), Saudi Arabia. Effects of solar radiation intensity, mass flow rate of the flowing air ((m) over dot(f)) and the length (L) and width (b) of the absorber plat on the flowing air outlet temperature (T-fo) and the heater instantaneous (eta(inst)) and daily (eta(d)) efficiencies were studied. To improve the heater performance, effect of using absorber plates coated with various selective coating materials on the heater performance was also investigated. The best performance was achieved using nickel-tin as a selective coating material with a daily average of the instantaneous efficiency of 0.46. To validate the proposed mathematical model, the simulated results were compared with the measurements that had been performed for the heater with a black painted absorber plate under Tanta, lat. 30 degrees 47' N (Egypt), weather conditions. It was found that the proposed model is able to predict the T-fo accurately with a daily average relative percentage error of 7.7%. It was also inferred that the annual average of eta(d) with a nickel-tin selectively coated absorber is higher than that with a black painted absorber by 29.23%. (C) 2009 Elsevier Ltd. All rights reserved.