Passenger airline

• Mainline airlines operate flights by the airline's main operating unit, rather than by regional affiliates or subsidiaries
• Regional airlines, non-"mainline" airlines that operate regional aircraft; regionals typically operate over shorter non-intercontinental distances, often as feeder services for legacy mainline networks
• Low-cost carriers, giving a "basic", "no-frills" and perceived inexpensive service
• Business class airline, an airline aimed at the business traveler, featuring all business class seating and amenities
• Charter airlines, operating outside regular schedule intervals
• Flag carriers, the historically nationally owned airlines that were considered representative of the country overseas.
• Legacy carriers, US carriers that predate the Airline Deregulation Act of 1978
• Major airlines of the United States, airlines with at least $1 billion in revenues