A U.S. airline's rank is determined by the amount of revenue it generates. It is then classified by the U.S. federal government and placed in one of three categories: major, national or regional. If you've flown before, it may be easy for you to tell the difference between the three categories.

Airlines are primarily classified into three main categories based on their revenue, route network, and service model: Major, National, and Regional. Major Airlines (like American, Delta, and United) are the giants of the industry, operating international networks with annual revenues typically exceeding $1 billion. National Airlines are mid-sized carriers that usually focus on a specific country or large geographic region, often operating as low-cost alternatives (like JetBlue or Spirit). Regional Airlines are the smallest, typically flying "feeder" routes for major airlines under brands like "American Eagle" or "United Express," using smaller turboprop or regional jet aircraft. Beyond these economic classifications, airlines are also categorized by their business model: Full-Service Carriers (FSC) offer multiple classes, meals, and lounges; Low-Cost Carriers (LCC) focus on point-to-point efficiency and unbundled pricing; and Charter Airlines operate non-scheduled flights for specific groups or tour operators. There are also Cargo Carriers (like FedEx and UPS) that exclusively transport freight rather than passengers.