There are many synonyms that can be used in place of the word "airgraphs," which refers to a type of letter that is delivered by airmail. Some possible options include airmail letters, aerograms, air letters, flying letters, and sky mail. Other terms that could be used to describe this type of correspondence might include express mail, priority mail, or expedited delivery. No matter which term is used, the basic idea remains the same: a type of letter that is sent quickly and efficiently over long distances, often using specialized air transportation services to speed up the delivery process.