Air Illinois is a regional airline that operated in the United States during the 1970s and 1980s. Synonyms for the term "Air Illinois" could include "Illinois-based airline", "Illinois air carrier" or "airline operating in Illinois". These alternatives highlight the geographic affiliation and nature of the airline. Additionally, synonyms such as "Illinois air transport company" or "Illinois aviation service provider" can also indicate the same concept. Overall, these synonyms help convey the idea of an airline specifically connected to the state of Illinois, providing air transportation services within or from the state.