Some sources claim that the T-48 designation was applied to a 1984 Cessna program for a modified T-37 Next Generation Trainer [NGT] program to replace the T-46,, but this is not widely attested. For some reason, the "T" (trainer) sequence, last seen in the Cessna T-47 in 1984, was restarted with the Beech T-1 Jayhawk in 1990. Further adding to the confusion is the fact that other trainer programs were given the designations T-49, T-50 and T-51.

The Wikipedia list is defective in several respects.

Wikipedia claims that there is a Boeing CT-49, though is not able to describe it. The NATO Airborne Early Warning & Control Force (NAEW&CF), activated 28 June 1982, consists of personnel of most NATO Air Forces, jointly operating seventeen E-3A AWACS aircraft. The NAEW&CF also has two [possibly three] CT-49As for training, which are B-707 airframes without the radar on top. In addition, the CT-49s are not capable of air-to-air refueling, but only can make “dry” hook-ups for training purposes. Luxembourg has no Air Force but for legal purposes NATO’s 17 E-3A Sentry AWACS aircraft and 2 Boeing CT/49 (training) have LU registration. The CT-49 is a designation by Boeing and/or the USAF for a militarized, cargo/trainer versions of the B-707-320C. NATO operates a fleet of such aircraft in the E-3A flight-crew training role and cargo/passenger transport role. Bearing the rather vague designation of TCAs (Trainer Cargo Aircraft) they are also designated NCT-49A, as can be seen in their technical orders. There are only a couple of SOURCES / SOURCES for this designation.

The T-50 is real, but it is a South Korean project.

Wikipedia also claimed that there was a Cessna T-51, but they failed to describe it and no one else had ever heard of such a thing. Eventually Wikipedia figured out that Titan Aircraft offers a 3/4 scale replica P-51 homebuilt kit, said to combine friendly low speed handling characteristics with agility and high performance, that is destignated the T-51 Mustang.