However, with aircraft the role of heredity has not been established although some of the type clubs will have some strong opinions on that topic. Heredity does seem to play a part in ADs that are issued against a particular aircraft. These frequently grow out of design decisions that may have been made decades ago. As a result of accident investigations and inspections, the FAA may issue an AD against a part that has shown to be a recurring problem. The age of the part frequently plays a role.
Stress cracks develop, seals fail, or corrosion begins.
The list is endless and frequently is as much a symptom of old age, and possibly inadequate maintenance, as of poor design. Periodic inspection and replacement of worn or time-limited parts keep small problems from becoming critical safety issues. An aircraft has not been built that doesn't require ongoing maintenance typically the more complex the machine, the more is needed to keep it airworthy. One of the big maintenance factors is retractable landing gear. It's pretty reliable when properly maintained, but valves, hydraulic lines, pistons, cylinders, uplocks, electric motors, and microswitches, as well as wiring, all wear much more faster than a solid piece of spring steel or an oleo strut.