Why does my Airport icon vanish?

A couple of years ago my Airport icon kept vanishing, until I disconnected the battery, pressed the start button, etc. Got fed up with doing this so bought a new card from iFixit and fixed it! Happy! Until yesterday that is, when I reinstalled my OS (because several apps were greyed out) and now no icon again! Tried the above and deleting the Airport and System Prefs .plists and even started a new account. Nothing. Still no Airport icon. Any ideas, please? Thanks in advance.