This is a useful site for finding archival records found in libraries and other special collections around the United States. Search for company names, company presidents, known designers and engineers.
John Chaknis Eastern Airlines strike collection, 1986-1990 (Georgia State University - Special Collections and Archives)
Northwest Airlines corporate records, 1917-1998 (bulk 1930-1994) (Minnesota Historical Society)
C.L. Woods papers, 1947-1969 (University of Wyoming - American Heritage Center)

This is a collection of links to various institutions with aviation and aerospace holdings from Embry-Riddle Aeronautical University. Some collections focus on the aviation industry in a specific state or region, while some like University of Miami Libraries, Special Collections include the records of Pan Am World Airways, Inc.

This collection ranks among the more unique treasures at the Library of Congress. It is comprised of both technical documents and illustrative material. Acquired by the Library in late June 1970 from Max Blondel la Rougery in Paris, material from this collection was originally used for L’Aérophile, a leading French aeronautical journal. Materials related to Amelia Earhart are found throughout the collection.

This is a museum but as part of the institution there is the Dahlberg Research Center includes the Harl V. Brackin Memorial Library and the Museum of Flight Archives. The Museum of Flight’s collection is considered one of the best air and space museum collections in the world. It includes over 150 aircraft, over 25,000 small objects (classified as anything smaller than an aircraft), over 90,000 books and periodicals, over 18,000 aircraft manuals and other technical documents, and nearly 5,000 cubic feet of archival materials, including over a million images.

They have a number of online resources available to explore the collection materials. For library materials, including books, periodicals and manuals, see the Library Catalog. For archival materials, such as historical documents, photographs, technical drawings, personal papers, and printed ephemera, see the Archives Research Portal. For digitized materials, see the Digital Collections website. They offer both in-person and remote research assistance via our Research Center.

The Museum's Archives Division holds personal and professional papers of individuals, corporate and organizational records, and artificial collections. There is a focus on the history of flight from ancient times to the present, and many emphasize technical aspects of aircraft and propulsion systems.

The National Archives contain the records of federal agencies including but not limited to: the FAA, National Transportation Safety Board (NTSB), NASA, Civil Aeronautics Board (CAB), National Advisory Committee for Aeronautics (NACA). There is a blog post that might be helpful in understanding the overall collections.

The NTL is run by the U.S. Department of Transportation.

The organization has historical and contemporary publications and records related to aviation and space history specifically for people and companies in the San Diego area. A number of the collections are military related, but they also have the Air France Menus Special Collection, some Charles Lindbergh papers, papers of Albert S. Menasco who was a key figure in the design of airplane engines, papers from Andrew Fodor who was a primary investor in the Mutual Aircraft Factory, AP Keith Personal Papers, and more.

To find more information search Archives West. Includes:
Boeing Airplane Company photograph collection 1927-approximately 1965
Convair Photograph Collection 1952-1957
Boeing Airplane Company records 1946-1968
There is also the Northwest Historical Annual Reports Collection which includes annual reports to shareholders for Boeing.

This is a labor oriented library and is good for strikes and negotiations oriented collections including:
Air Line Pilots Association (ALPA). Records, 1965-1975. Air Line Pilots Association President's Office
William C. Davis (Papers, 1931-1972) Minutes, agendas, conference materials, financial files, and reports, relating to Davis's activities as an official with Air Line Pilots Association
Robert L. Tuxbury (Papers, 1936-1970) Correspondence, minutes, reports, manuals, clippings, and other materials, relating to Tuxbury's activities with Air Line Pilots Association.
Charles T. Hawkins (Papers, 1956-1977). Minutes, agreements, mediation reports, fact-finding exhibits, and other material, relating to Hawkins's activities with Air Line Pilots Association.
J. Harrill Wylie (Papers, 1942-1970) Correspondence, newsletters, reports, office files, arbitration hearing transcripts, and exhibits, relating to Wylie's activities involving the merger between Capital Airlines and United Airlines (1960-1964) and with Air Line Pilots Association.