This page is written to address a potential problem that many older airplanes face. In many older aircraft production runs, AD's were issued to specific components of the plane, with applicability based on the serial number of the aircraft. This was acceptable at the time, prior to the "mixing" of airplanes and their many interchangeable components. In today's fleet it has been our experience that these serial number applicability guidelines are unreliable in determining AD compliance. We suggest that all AD's for your series of aircraft be researched for potential un-airworthy conditions. Don't forget to have an up to date Airworthiness Directive Compliance List in your Aircraft Maintenance Records.