The aviation industry may be divided along three lines: commercial, general, and military.

Commercial Aviation

Commercial aviation includes the airlines, air taxi and charter operations, airplane rental, and aerial applications. Commercial aviation is further broken down according to the size of the company. Mainline national carriers are airlines that earn between $100 million and $1 billion per year. Regional carriers have revenues of less than $100 million each year. Mainline carriers use large passenger jets (more than 90 seats) and regional carriers use smaller piston, turboprop, and regional aircraft (up to 90 seats). Other commercial uses for aircraft include forest fire containment, crop dusting, and aerial signage. Helicopters are used for police, emergency, rescue, and passenger services, and for traffic reporting. In 2018, there were 19,624 airports in the United States, including 5,090 public, 14,249 private, and 278 military airports.

General Aviation

General aviation encompasses personal and instructional flights and business and executive aircraft. General aviation also includes smaller crafts, such as ultralights. Most of the airplane activity in the United States occurs in general aviation. General aviation aircraft fly about 25 million hours, approximately two times the commercial airline flight hours. There are nearly 3,000 general aviation airports in the United States, but general aviation craft fly into and out of most of the country's approximately 19,624 airports. Airports range in size from a single unpaved landing strip to complex sites of 20,000 acres or more.

Military Aviation

All branches of the U.S. armed forces, but especially the U.S. Air Force, rely on planes and helicopters and employ soldiers and civilians to pilot, manage, and maintain their vehicles and equipment. Many commercial pilots receive training and experience in the military before going to work for civilian airlines. Many military air vehicles, which often incorporate advanced technology, are designed for combat or the transport of cargo and personnel. In December 2018 the Congressional Budget Office estimated that, in 2018 dollars, it would cost about $15 billion annually to replace aircraft in the U.S. Air Force fleet during the 2020s. This figure was projected to increase during the 2020s, reaching $23 billion, but decline to $15 billion during the 2040s.

Airports

Large airports have often been compared to cities. Each has its own police force, fire department and emergency rescue service, retail stores and restaurants, maintenance crews, warehouses for cargo, and even its own transportation system. A large airport may employ thousands of people. Many airports are managed by fixed-base operators (FBO). The FBO is often responsible for the entire operation of the airport, including its management, fueling, hangar, and repair facilities. A feature at many airports is the control tower. Air traffic controllers regulate the flow of traffic into and out of the airport. Additional air traffic control centers are spaced along the airways, linking the entire system. Other important features of larger, international airports and airports located near the country's borders are the customs and immigration departments. More than 100 airlines make use of these airports.

Airlines

The typical organizational structure of an airline includes operations, maintenance, marketing, and finance divisions. The operations division manages the day-to-day activities of the airline, overseeing the pilots and flight attendants, the flight dispatchers, flight scheduling, and ground crews. The maintenance division handles the avionics and mechanics of the airplane, performing daily inspections, and routine repairs and maintenance, such as filling the tires with air and fueling. The marketing department sells the airline's services as well as creates new programs, services, and advertisements to attract customers. It also takes ticket reservations and purchases. The finance division is concerned with maintaining a smooth cash flow to ensure the airline's continued success. Other areas of an airline may include an interior design staff to develop the passenger areas of a plane and clothing designers to design the uniforms of the pilots, flight attendants, check-in personnel, and others.

Cargo

Airlines carry more than just people. Transportation of cargo, from single packages to shipments such as 25-ton printing presses, complete oil well towers, and heavy construction equipment, is an important source of income. The use of airplanes to transport fresh fruits, vegetables, and seafood has had a great impact on the variety of foods available for people to eat. Other industries, such as the auto industry, transport parts and components by air so that they arrive at their factories just when they are needed. An added source of revenues is transportation of mail and packages, which may contribute as much as 15 percent to a major carrier's earnings. There are now many companies that specialize in mail transport, some with their own fleets of airplanes. A typical airplane carries a variety of cargo, along with its passengers and crew. Air cargo airlines were increasingly busy from 2003 through 2008, according to a report by the Bureau of Transportation. The total air cargo revenue grew steadily in that time span, from 56.4 million ton-miles in 2003 to 68.5 million ton-miles in 2007. Business started to decline in 2008 and 2009, reaching a low of 54.8 million ton-miles, but has rebounded since. Air cargo revenue for 2014 exceeded 65.0 million ton-miles, and continued increasing through the end of the decade, reaching 79.8 million ton-miles in 2018, an increase of about 5 percent from 2017.

Aircraft Manufacturers

An important component of the airline industry is the aircraft manufacturer. The major carrier aircraft manufacturers in the United States are Boeing Aircraft Company and Lockheed Martin. They also build aircraft, weapons, vehicles, and components for the military and the U.S. space program. Much of their work involves the research and development of new technologies. Many features of the modern airplane were first developed for the military or the space program and were later adapted for commercial aircraft. A typical aircraft manufacturer employs people from nearly every field, from physicists, biologists, engineers, technicians, and mathematicians to accountants, lawyers, writers, and artists, as well as traditional manufacturing personnel. Many other manufacturers provide essential aircraft components and electronics.

A number of manufacturers concentrate on supplying aircraft to the general aviation industry. Major general aviation manufacturers include Piper Aircraft, Cessna Aircraft Company, Raytheon Company, Bombardier, and Gulfstream Aerospace Corporation. Still other manufacturers build helicopters. The growing popularity of ultralight aircraft, many of which are built by the purchaser from a kit, has created more manufacturing opportunities. The popularity of skydiving also has increased the need for such equipment as parachutes and safety harnesses.

Federal Aviation Administration

The Federal Aviation Administration oversees the airline industry, performing a number of important functions. Aircraft and airports must meet rigid specifications for safety, performance, noise, and pollution standards. Routine inspections of each aircraft alert airlines to faults in their aircraft and keep unsafe airplanes from the sky. The FAA establishes training and licensing requirement for pilots, instructors, and other workers. The FAA also hires, trains, and assigns air traffic controllers to manage the traffic flow above airports and across the country. Most of the current air traffic control system in the United States has been in place since the 1960s. As its computers and other components have aged, and even become obsolete, the FAA has begun to rebuild the system, sponsoring research and development into new components that will be able to regulate air traffic for many years to come. The FAA also governs the design, construction, and operations of airports. Everyone who flies remains subject to the FAA's rules and regulations.