By the end of World War II the Mustang was being used in every theater of operations by the Army Air Force.
After the jump, a look at a China based P-51B.
The 23rd Fighter Group was the direct descendant of the Flying Tigers. In July of 1942 the “American Volunteer Group” was absorbed into the US Army Air Force and became the 23rd Fighter Group. They would continue to fly P-40s for quite some time, but by mid-1944 Mustangs were starting to show up in theater.
This particular aircraft was flown by Major John “Pappy” Herbst. He had first joined the Royal Canadian Air Force in 1941, and claimed a Bf109 while serving in the Mediterranean. The next year he would transfer to the Army Air Force, and by 1943 he was serving as an instructor at a Transition School for new pilots in brand new Merlin Engined Mustangs. Apparently he made an impression with a spectacular and illegal aerobatic display that led to his assignment to China. At some point he picked up the nickname “Pappy” since he was in his mid-30s with a wife and kids; not typical for a World War II fighter pilot!
When he first reported to the 23rd Fighter Group in 1944 he was issued a worn out P-40. But after quickly scoring four kills he was upgraded to a P-51B. The serial number is unknown, but it was apparently an early “B” model that had been upgraded with the long range fuselage gas tank. And that is the plane shown here. He scored 11 kills with it in the Fall of 1944; and three more kills in other Mustangs (apparently one in a “D” model). 14 kills ties him for top Mustang Ace in China (with Edward McComas).
This is the Tamiya kit with Aeromaster Decals. The DF Loop antenna on the rear fuselage was sourced from an old Monogram Do335 kit. This model was the subject of my “Simple Build” project. “Tommy’s Dad” was one of the best known CBI aircraft late in the war; and I was excited to show a plane with such understated markings.
Major John “Pappy” Herbst. Commander of the 74th FS, 23rd FG.
Plane Dave 
I always liked the B and C’s style, the razorback fuselage. The D was the better aircraft , better visibility bubble canopy, 6 in place of 4 canted jam prone 50’s. But the P51B and P51C with the stock hood and the Malcom hood looks good, (it was slightly faster too).
I think the whole family of Mustangs look pretty terrific! I believe the jamming problem was fixed with a motorized ammunition feed, even before the “D” introduced the strait feed path.
One thing I read about the older Mustangs makes laugh. When the “D” models were first introduced they were typically claimed by Squadron and section leaders because of the better visibility and other details fixed. But after several months the process started to reverse itself, and B/C models were more often claimed by senior pilots. Even with 200 less horsepower the B model was a bit faster. So even if the bubble canopy looks great, it adds aerodynamic drag.