The deregulation of the airline industry in the United States in 1978 eliminated governmental control over most business practices of airlines. However, the federal government continues to regulate certain practices for the protection of the airlines' customers, in addition to its long-standing role in overseeing air safety. Congressional interest in the rights of airline passengers became intense between 2007 and 2009, when a series of delays stranded passengers aboard airplanes at U.S. airports for 10 hours or longer. Since then, Congress has strengthened passengers' rights under federal law, and many Members of Congress have continued to follow aviation consumer issues closely. This report examines aviation consumer protections in the post-deregulation era. It explains the roles of Congress and the U.S. Department of Transportation (DOT) in protecting airline consumers, and discusses some major passenger rights issues and related laws and regulations. The rights of domestic airline passengers are set forth at three different levels: in federal laws, in regulations, and in the airlines' own policies. Congress, under its constitutional power to "regulate Commerce with foreign Nations, and among the several States," has authority over airline passengers' rights. State and local governments are generally preempted by law from regulating "price, route, or service of an air carrier." By and large, the rights of airline passengers are defined by Congress. Congress determines the extent to which airline consumer rights are codified in law, authorizes federal agencies to enforce those rights, and directs or authorizes federal agencies to define and enforce passenger rights that are not specifically enumerated in legislation. The House Committee on Transportation and Infrastructure and the Senate Committee on Commerce, Science, and Transportation are the primary congressional committees of jurisdiction, and exercise routine oversight over DOT, the principal department responsible for executing and enforcing airline passenger rights laws. In many cases, Members of Congress become aware of passenger rights issues by receiving complaints from constituents, and congressional office staff members are often called upon to advise constituents about their rights as air passengers, to provide guidance on filing complaints with DOT, and to communicate with DOT about constituent concerns. The controversy surrounding tarmac delays illustrates the ways in which Congress exercises its oversight authority. Between 2007 and 2009, hundreds of incidents occurred in which passengers were held aboard planes that had either departed airport gates but were not allowed to take off or had landed but were not allowed to disembark passengers. These incidents were extensively reported in the news media, and congressional offices received numerous complaints from constituents who had been aboard planes that were unable to provide passengers with drinking water or on which lavatories stopped functioning. Congressional hearings ensued in 2009. In the wake of this attention, DOT issued rules on tarmac delays in 2010. Language on this subject, providing a firmer statutory footing for the federal rules that had already entered into effect, was incorporated into the FAA Modernization and Reform Act of 2012 ( P.L. 112-95 ). The 2016 FAA reauthorization incorporated language that defined excessive tarmac delays, but also altered how the tarmac delay threshold is measured, which could afford airlines more leeway in dealing with delayed flights. Some Members of Congress also have expressed concern about issues related to flight schedules, aircraft capacity, and frequency of service. Although these matters are no longer subject to federal regulation, they are often raised in the context of business dealings between air carriers that do require federal approval, such as mergers and code-share arrangements. For example, the proposed merger between American Airlines and US Airways led to objections that the combination would reduce competition and limit consumer choices. These concerns were expressed by some Members of Congress and witnesses during congressional hearings in February and March 2013, before completion of the merger in December 2013 and the final court approval of a settlement between the airlines and the U.S. Department of Justice Antitrust Division was granted in April 2014. DOT is responsible for executing and enforcing airline consumer rights laws established by Congress. It may also develop regulations based on more general statutory authority, giving it broad powers to prescribe regulations, standards, and procedures related to air travel. More specifically, DOT has authority "under 49 U.S.C. Section 41712, in concert with 49 U.S.C. Sections 40101(a)(4), 40101(a)(9), and 41702 to protect consumers from unfair or deceptive practices and to ensure safe and adequate service in air transportation." DOT's authority in this area is exercised by the Office of the Secretary, not by the Federal Aviation Administration (FAA), which is responsible for aviation safety. DOT does not have authority over matters related to aviation security and airport security screening, which are administered by the Transportation Security Administration (TSA), an agency of the Department of Homeland Security. DOT's statutory authority is generally used as the basis for rulemaking. Occasionally, it is also used in direct enforcement actions. Most of DOT's consumer rules are based on the "unfair or deceptive practices" provision, with a few based on the "ensure safe and adequate service" provision. The definition and interpretation of the phrase "unfair or deceptive practices" can significantly affect the scope of DOT's rulemaking and enforcement authorities. Separately, DOT enforces regulations to ensure that individuals with disabilities have nondiscriminatory access to the air transportation system, and that airlines do not subject passengers to unlawful discrimination on the basis of race, gender, religion, or national origin. The DOT Aviation Consumer Protection Division's booklet Fly-Rights: A Consumer Guide to Air Travel is published online. It covers a wide array of topics, from flight delays and cancellations to travel scams. It also provides information about DOT rules on consumer complaints. The Office of the Assistant General Counsel for Aviation Enforcement and Proceedings in DOT (OAEP), including its Aviation Consumer Protection Division, monitors airline compliance, investigates reported violations of DOT regulations, and enforces rules and regulations. It may negotiate consent orders with air carriers and fine violators. In 2015, DOT issued 15 consent orders related to aviation consumer rule violations and assessed $2,435,000 in civil penalties. OAEP considers a number of factors in determining the civil penalty it would seek in an enforcement proceeding, such as the harm caused by the violations, the alleged violator's compliance disposition, the alleged violator's financial condition and ability to pay, how long the violations continued, and the strength of the case . Currently, air carriers are subject to a maximum civil penalty of $32,140 per violation, under 49 U.S.C. §46301 and 14 C.F.R. §383. Small businesses or individuals are subject to a maximum penalty of $1,414. Notwithstanding this limit, small businesses and individuals are subject to higher maximum penalties for discrimination ($12,856 per violation) and for engaging in unfair or deceptive practices ($3,214 per violation). OAEP may look into possible violations based on complaints from individuals, groups, other government agencies, or its own staff members' observations and research. Usually, its first action is to send a letter to the air carrier, setting forth the complaint or issues involved and requesting a response. This gives the air carrier a chance to look into the matter and to resolve the complaint, deny the complaint, or provide an explanation. This may be the end of the process, but OAEP may issue a warning letter if it concludes violations occurred but were inadvertent or minor. If OAEP believes enforcement action is appropriate, it would seek a civil penalty and consent order. A consent order typically relates the facts of the case to law and regulation, sets forth the penalty the violator has agreed to pay, and incorporates language ordering the air carrier to cease and desist from further violations. If the air carrier refuses to settle, the case may go to an enforcement hearing before a DOT administrative law judge. DOT also may request injunctive relief from a federal district court, although this is unusual. The third source of airline passengers' rights is each air carrier's "Contract of Carriage," the legal agreement between an airline and its ticket holders. Contracts of carriage typically define the rights, duties, and liabilities of parties to the contract. For example, United Airlines' contract of carriage lists 30 rules, covering matters from reservations and ticketing to cancellation and refund policies to medical ground transfer services. Before the age of electronic tickets, contracts of carriage were usually evidenced by standard terms and conditions printed on the reverse of paper tickets. Now, they are often available for download via airlines' websites or at an airline's ticketing facilities. Passengers may take legal action in federal courts based on the contracts. Contracts of carriage replace the pre-deregulation-era-rules "tariffs" that were subject to approval by the Civil Aeronautics Board (CAB) . The CAB could take action against an air carrier that violated its approved tariffs. Since the economic deregulation of the domestic airline industry in 1978, the federal government no longer has control over airlines' prices or routes, and contracts of carriage are not subject to federal review or approval. However, a contract of carriage that conflicts with federal laws or regulations may not be enforceable by the airline. With respect to passenger rights, the deregulated environment differs from the former regulated environment in two major ways. First, under regulation, the CAB had authority to approve carriers' proposed fares and even to set fares itself. The airlines' profitability was protected by this price setting and by barriers to the entry of new competitors. Airlines, for the most part, competed on service and frequency rather than price. Since deregulation, and especially with the advent of low-cost carriers, the primary means of competition has become price, not service. In recent years airlines have "unbundled" their offerings, charging separately for services that once were included in the price of a ticket. Among these charges are fees for checked baggage, early/priority boarding, and seat change on a flight. Such ancillary fees have become major causes of consumer complaints.