The thing is, even aircraft that are long retired can (and often do) have classified elements about them, the F-14 being case in point. The newness of the aircraft is often not the determining factor in the classification of it's systems. The items on the F-15C that were classified in 1991 and earlier (TEWS, ECCM, EWWS, EID, NCTR, radar frequencies, radar performance, AIM-7M, 9M Performance etc) are still pretty much classified today. New systems which have emerged since then such as JTIDS/FDL, JHMCS, Sniper Pod aren't classified at the user operator level, save for the odd mode e.g Sniper Air-to-Air functions.