Good background information may be found in reference sources.
Reference sources (dictionaries, encyclopedias, manuals, guides) provide the following types of information on virtually any topic:
Find additional reference sources by searching LVC Books. Click on Advanced Search,click on Type, choose Reference, and search for your keywords.
Image source: Four F-15 Eagle pilots from the 3rd Wing walk to their respective jets at Elmendorf Air Force Base, Alaska. U.S. Air Force photo by Tech. Sgt. Keith Brown. Public domain. Wikimedia Commons.