Air line is a term that is commonly used to refer to an airline or an aviation company. However, there are several other synonyms that can be used interchangeably to refer to air travel services. Some of the popular synonyms for air line include an air carrier, air transport, airline company, aviation firm, and air service provider. These synonyms are often used in the context of air travel and serve the same purpose as air line. They provide transport services to passengers and cargo through the use of airplanes. The use of different synonyms for air line helps to vary language usage and avoid repetition of words.