Most Widely Used Training Aircraft?

I would assume the most widely used would be the PT  ( Primary Trainer ) such as the PT-13, PT-19, etc. because all cadets learned initial flying in them. After graduating primary, some were sent to single-engine advanced, some to dual-engine, etc, but ALL started in the primary trainers.

Pilot training in WWII was a four step process:  primary, basic, advanced, and transitional training.  The aircraft used continued to change throughout the war.  Here is a good page that summarizes the variety used at each step in the process:  http://scharch.org/Dick_B...AAF%20Training/AAF.htm
 
For primary and basic pilot training, the planes used would be the same regardless of the ultimate type the pilot would fly.  It is with the third stage, advanced pilot training, that pilots would be differentiated between those to be trained for single engine airplanes from those being trained for multi-engine airplanes.  Those slated to fly multi-engine bombers or cargo planes (or the P-38 fighter) learned to fly two-engine planes in advanced training.
 
After advanced school, the pilot would then go onto transition school, which taught them on the specific aircraft they would be specialized for.
 
Kevin Anderson
'whose uncle was a WWII B-25 combat pilot

 
This is a Postcard that my Uncle Charlie sent to my father(then about 11 years old) during his training.
My father was a chubby kid hence his nickname.
 
Glenn
 
2nd Lt. Charles Spiegel
451st BG, 724th Sq.
KIA 12/29/44
Udine, Italy

Great responses thank you.
 
Glenn - beautiful postcard! Thanks for posting it here.
 
Steven out of interest did the B-24Es have a similar appearance in to the B-24Ds? Greenhouse in the nose?
 
I want to represent a few levels of aircraft from smallest / training aircraft up to a later Liberator combat variant, probably an 'H' or 'J'. I think i'll go for the Vultee either the 'Valiant' or the 'Vibrator' Like the look of them and the nicknames are a bonus.
 
Regards,
Evan