It is a changeable item, generally accessed through maintenance terminals (there are several PMAT ports, three of which are only accessible on the ground) or the primary MAT located in the cockpit, however access to specialized software (GBST) is required in order to create encoded data disks for upload. In addition, while some LRU's can be manually put into 'ground' mode, the central areas of the AIMS system require the air/ground logic to be in ground mode
@vapilot. What about the possibility of spoofing, rather than changing, the identifier?