SPD is an international shipping company based in iran and has a good reputation for the sake of The speed of services and fast delivery of cargoes between Iran and other countries. "Speed" is the key concept and the essence of the bussiness which should have been quickly captured through its logo.
On the other hand the logo should not have mentioned any of the methods of shipping because the company is active in all three lines of land, air and sea transportation.
Thus, The logo is designed by simplifying the body shape of a bird as a symbol of movement and speed and The sharp angle of the letters creates a sense of acceleration.