You can often see pilots in the cockpit from the terminal windows perform their pre- or post-flight checklists. You will notice they are often looking up and reaching for switches or knobs located over their heads. Those pilots are working with the ‘overhead panel’ that contains controls for various aircraft operating systems.
Those buttons, switches, and knobs are placed there for ease of cockpit workload management, and to be out-of-the-way of the more crucial flight controls, throttle quadrant, and main instrument panel.
Although the specific design and layout of overhead panels vary with each manufacturer and aircraft type, controls located on that panel are generally for pressurization, internal and external lighting, circuit breakers, and electrical systems including aircraft power source (external ground power, onboard auxiliary power unit, or engine generators).
All switches and knobs on the overhead panel are specifically designed with different and distinctive sizes and shapes for ease of operation in an emergency.
