Spark plugs are essential for igniting piston engines. Designed to deliver a pulse of electric current from the ignition system to the combustion chamber, internal combustion engines require the use of a spark plug to set alight aerosolized fuel. In aviation, a spark plug is typically housed out of sight at the top of a cylinder head and can easily go unchecked if maintenance is irregular. Resulting in poor engine performance, loss of power, or a critical accident if the component is failing, it is imperative that routine spark plug inspections are not dismissed. To better understand how spark plugs function in aircraft, we will dive into their application types, how each works, and their common errors.