1. A method for enabling creation and maintenance of inventories of data elements available on an aircraft fleet, the method comprising: accessing aircraft telemetry data from avionics equipment on a plurality of aircraft, the aircraft telemetry data comprising physical-layer datasets, wherein a first subset of the physical-layer datasets uses a first physical-layer protocol and a second subset of the physical-layer datasets uses a second physical-layer protocol that is different from the first physical-layer protocol; generating, with a processing system, decoded data elements by decoding the physical-layer datasets accessed from the avionics equipment, wherein the decoded data elements have a common protocol and format; generating, with the processing system and from the decoded data elements, derivative data elements, wherein at least one of the derivative data elements corresponds to both the first subset of the physical-layer datasets using the first physical-layer protocol and the second subset of the physical-layer datasets using the second physical-layer protocol; and creating, with the processing system, an inventory comprising the derivative data elements stored in a data structure that is available for use by the plurality of aircraft.