Museum libraries and archives are very helpful when it comes to this research, in my experience. They've got a whole process on getting the rights requests, reproductions, & fees.
These museums have specific research departments to help with this kind of stuff:
Smithsonian National Air & Space Museum: https://airandspace.si.edu/archives
National Naval Aviation Museum: https://www.navalaviationmuseum.org/emil-buehler-library/
National Museum of the United States Air Force: https://www.nationalmuseum.af.mil/Collections/Research/
National Archives: https://catalog.archives.gov/ (not strictly aviation and might not be as useful)