I was browsing the National Archives site and looking at some of the photos and films they have digitized. I am surprised how little they have on line.
However, I ran across some newsreels that apparently covered the “shuttle missions” where US bombers and fighters flew from England, attacked Germany, then flew on to Russia. Only the first two minutes of each newsreel is digitized.
Here is a screen capture from one of those newsreels. It is an interesting shot of one of the escorting P-51s.

P-51 on shuttle mission