Albert,
I believe this may be what you are after:
When providing aircraft type on a flight plan, pilots/operators are required to include information about the on-board, certified equipment using an identifier code as a suffix to the equipment type. For example, "B739/J" means a Boeing 737-900 with "Flight Management System (FMS) with DME/DME and IRU position updating and RVSM." ATC sometimes request confirmation of the eqiupment fit code.
A full list of codes is available here:
FlightAware > FAQs > Aircraft Equipment Suffixes