The aircraft are brought into the class by common similarities. For instance, to be brought into the class called Boeing 747 cargo door crashes, all Boeing 747s that have crashed must have had a sudden loud sound on the cockpit voice recorder. If not a sudden loud sound on the CVR tape then that crashed Boeing 747 is excluded from the class. Deductions can then be made about each member of the class based upon similarities with the other members. For instance, if three members of the group have inflight damage to the right wing fillet, then it can be deduced that aircraft number four probably has inflight damage to the right wing fillet.
All deductions are subject to visual confirmation if possible.
In addition, once the members of a group are defined, then inductions can be made about potential members of the group. For instance, if all the damaged aircraft in the group had outward opening cargo doors, then similar aircraft with outward opening cargo doors are at risk of becoming a member of the crashed group, subject to other similarities being the same, such as high flight time and same model aircraft. The method used to group the aircraft into one crashed group instead of four separate crashes has been to review the various government accident reports, news reports, eyewitness accounts, personal experience, and other official documents. The main documents used are on the web site and are the accident reports from the governments involved, UK, USA, India, Canada, and input from Ireland, New Zealand, and France. Every statement from which conclusions are drawn is supported by evidence or reputable eyewitnesses.