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 performing operations comprising: accessing (i) a first decoding rule for translating the first physical-layer protocol into a common protocol and format and (ii) a second decoding rule for translating the second physical-layer protocol into the common protocol and format, translating the first subset of the physical-layer datasets accessed from the avionics equipment into a first subset of the decoded data elements having the common protocol and format by applying the first decoding rule to the first subset of the physical-layer datasets, and translating the second subset of the physical-layer datasets accessed from the avionics equipment into a second subset of the decoded data elements having the common protocol and format by applying the second decoding rule to the second subset of the physical-layer datasets; generating, with the processing system and from the decoded data elements, derivative data elements that are globally applicable to each of the plurality of aircraft, wherein generating the derivative data elements comprises: identifying a first measurement unit in the first subset of the decoded data elements and a second measurement unit in the second subset of the decoded data elements that is different from the first measurement unit, and transforming the first subset of the decoded data elements and the second subset of the decoded data elements into the derivative data elements such that the derivative data element have a common measurement unit, 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.