Most of the photos on this site were extracted from reference images (high-resolution tiffs, 20 to 200 megabytes in size) from the Library of Congress research archive. (To query the database click here.) Many were digitized by LOC contractors using a Sinar studio back. They are adjusted by your webmaster for contrast and color in Photoshop before being downsized and turned into the jpegs you see here.

B-29 bombers flying in the "Combat Box" formation. Air Force photo scanned from the original negative. View full size.
I was told this was taken by an Air Force photographer who served from 1944-48 so you're right about the dates.
Red stripes (as in this photo) were added to the white horizontal bar on the US national aircraft insignia in January 1947.
Black undersides were used on many B-29s against Japan in WW2 and later on in Korea.
"United States Air Force" was marked across the front, upper part of the fuselage on all aircraft after 1950. I don't see it in this photo but it might be the photo's perspective is too low to see it if it is there. Or, it might not be there.
The photo is probably post-1947. It might be pre-1950.
The Army Air Corps ceased to exist in January 1942. The U.S. Army Air Forces became the new entities for Army aviation until 1947 when the USAF became a separate service. Since the bottoms of some of B-29's are black this would date the image around the Korean War.
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