Transport unit code letter allocations

You might try the book "Air Force Colors, Volume 3, Pacific and Home Front, 1942-47".  Here are some Troop Carrier aircraft numbers from the 5th AF in that book:
6-25, 39th Troop Carrier Squadron (317th TCG)
26-50, 40th Troop Carrier Squadron (317th TCG)
51-75, 41st Troop Carrier Squadron (317th TCG)
76-99, 46th Troop Carrier Squadron (317th TCG)
101-125, 55th Troop Carrier Squadron (375th TCG)
126-150, 56th Troop Carrier Squadron (375th TCG)
151-175, 57th Troop Carrier Squadron (375th TCG)
176-199, 58th Troop Carrier Squadron (375th TCG)
201-225, 65th Troop Carrier Squadron (Attd 433rd TCG)
226-250, 66th Troop Carrier Squadron (Attd 433rd TCG)
300-325, 67th Troop Carrier Squadron (433rd TCG)
326-350, 68th Troop Carrier Squadron (433rd TCG)
351-375, 69th Troop Carrier Squadron (433rd TCG)
376-399, 70th Troop Carrier Squadron (433rd TCG)
401-425, C Flight (317th TCG)
500-525, 6th Troop Carrier Squadron (374th TCG)
526-550, 21st Troop Carrier Squadron (374th TCG)
551-575, 22nd Troop Carrier Squadron (374th TCG)
576-599, 33rd Troop Carrier Squadron (374th TCG)
600-630, 5th Combat Cargo Squadron (2nd CCG)
631-660, 6th Combat Cargo Squadron (2nd CCG)
661-690, 7th Combat Cargo Squadron (2nd CCG)
691-720, 8th Combat Cargo Squadron (2nd CCG)
 
As far as I can tell, the CBI Troop Carriers did not use this same numbering system.

Tom -
Book 5th Air Force Story by Kenn Rust
1945 - The 317th TCG and the 375th TCG added an
X Prefix to their Aircraft Number.
Photo of 375th TCG C-46 X163 " Quivering Sal "
Photo of 317th TCG C-47s  X6A  ,  X13A
Mike 
 

In Oct 1944, the prefix "X" was added to 54th Troop Carrier Wing aircraft numbers by order of that unit.  The 5298th Troop Carrier Wing (Prov) ordered a "W" above the center digit in it's numbers.  On 30 Dec 44, the 5298th TCW (P) became the 322nd TCW.  The 374th TCG was the only group assigned to the 5298th/322nd TCW, thus the only planes with a "W".  In May 1945, the 322nd TCW dropped using 500-series numbers and started using last four digits of the serial number.
Numbers in the 800-900 range were assigned to aircraft belonging to Service Groups.

Mark          "Still putting out" W804 was from the 4th Air Service Area Command ; it had a arrowhead design behind the cockpit with " IV ASAC" on. The camouflage was removed rom the cowlings and they were polished.
Regards
Nick
 
 
 
 
 
 
 
 

The book shows a C-46 of the 374th TCG with a "W" over "8347" on the tail.  This number would be last 4 digits of the serial number which occured after May 1945, as I mentioned before.  It also could be an aircraft assigned to a Service Command or Group, before May 1945.
Service Units had numbers in the range 800-900 prior to May 45.
I have no further information on this subject.  Maybe I should go back to my favorite forum, Ground Units.

No, the Ground units forum is no more helpful on this matter than any other.  If I didn't have the book "Air Force Colors, Vol. 3", I would have been clueless.  I think this book is still available for sale, so check Barnes & Noble or Amazon.  It's very good for identifying Bombers, Fighters, Transports, and other aircraft from all over the Pacific, the CBI, and CONUS.

One C-47 coded X158 was 43-16327 but I'm not sure whether that was "Tail Wind" or not.  Similarly one X159 was 43-16296 but that was named "Bad Landing" on the RHS and whether it was "Jet Propelled" (not Propeller) on the LHS I don't know.  Maybe someone else can comment on that?  You list "Airborne Repair Shop 5" as an alternate name for "Bye, Bye, Blues"; where does that name appear please?
 
Regards,
Dave