Allegheny Airlines was a regional airline that operated out of Pittsburgh, Pennsylvania, from 1952 to 1979 with routes primarily located in the eastern U.S. It was the forerunner of USAir that was subsequently renamed US Airways, which itself merged with American Airlines. Its headquarters were at Washington National Airport in Arlington County, Virginia.
 Allegheny Airlines began as All American Aviation Company providing mail delivery starting on 7 March 1939. It was founded by du Pont family brothers Richard C. du Pont and Alexis Felix du Pont Jr.
 In 1949 the company was renamed All American Airways as it switched from air mail to passenger service. On 1 January 1953 it was again renamed, to Allegheny Airlines. Like other local service airlines, Allegheny was subsidized; in 1962 its revenue of $23.5 million included $6.5 million in "public service revenue".
 In 1960, Allegheny headquarters were in Washington, D.C.
 In 1953 Allegheny's network blanketed Pennsylvania, reaching Newark NJ to Cleveland and Huntington WV. It added Detroit (YIP) in 1956, Boston in April 1960, La Guardia in 1964, Norfolk in 1966, Toronto in 1967, and Louisville-Nashville-Memphis in 1968. The Lake Central Airlines merger in July 1968 added Chicago and St Louis, and the Mohawk Airlines merger in April 1972 added Montreal, Minneapolis and many New York cities. Houston in 1978, then Florida at the end of 1978 (TPA-MCO-PBI) and Phoenix in 1979.
 In 1959 Allegheny debuted its first turbine airliner—a Convair 540, a Convair 340 with the piston engines replaced by Napier Elands. When Rolls-Royce bought Napier it dropped the Eland, so 540s in the United States reverted to piston; Allegheny's last 540 flights were in 1962. The airline bought new Fairchild F-27Js that the company named "Vistaliner". The F-27J was a U.S.-built version of the Fokker F27. The airline switched to General Motors/Allison turboprops in the Convair 580 which the carrier named the "Vistacruiser", the first CV580 flight was in June 1965. The last DC-3 flights were in 1962 and the last piston flights were in 1967.
 In 1965 Allegheny announced it would add the first jet aircraft type to its fleet—the Douglas DC-9-10—which the airline stated would be placed into service in 1966. Allegheny then added other jets, notably the McDonnell Douglas DC-9-30 which the company named the "Vistajet". Later jets included Boeing 727-100s, 727-200s and McDonnell Douglas DC-9-50s. The Mohawk merger added British Aircraft Corporation BAC One-Eleven jets to the fleet as well.  Allegheny Airlines was also the first airline with a network of affiliated regional airlines, the Allegheny Commuter system, which began with Henson Airlines in 1967.
 As deregulation dawned, Allegheny, looking to shed its regional image, changed its name to USAir on October 28, 1979.
 After Allegheny Airlines rebranded itself as USAir, the company retained its earlier name for its Allegheny Commuter service until 1989 when it became US Airways Express.
 Under USAir, which eventually renamed itself US Airways, the Allegheny name continued to be used by the parent company, keeping the trademark under US Airways' control. Suburban Airlines was originally headquartered at the Reading Airport in Reading, Pennsylvania, and flew a large fleet of Short 330s and Short 360s, being the launch customer for the Short 360. It had three Fokker F27s, and was the last US operator of passenger F27s. After replacing much of its Short fleet with de Havilland Canada DHC-8 Dash 8s and retiring the F27s, Suburban merged with another wholly owned USAir subsidiary, Pennsylvania Airlines, which was headquartered at Harrisburg International Airport near Harrisburg, Pennsylvania. The combined airline retained the historic Allegheny Airlines name until it was merged with another wholly owned subsidiary, Piedmont Airlines. The subsequent airline retained the Piedmont Airlines name. After retiring earlier aircraft, Allegheny, before and after its mergers, mainly flew De Havilland Canada Dash 8s to 35 airports in the northeastern United States, and eventually Canada, from hubs at Boston and Philadelphia. Its activities and Activities Dash 8 fleet were incorporated into a regional airline, Piedmont Airlines, in 2004.
 As of October 2023 an American Airlines Airbus A321, registered N579UW, is painted in Allegheny colors. It recently was on an Airbus A319 registered N745VJ, before being repainted into standard American livery in March 2023 and US Airways also operated this aircraft with a retro Allegheny Airlines paint scheme.
 This is a list of cities served by Allegheny Airlines until October 1979. It does not include destinations served before that year. Allegheny flew to dozens more cities at some point, including Erie, Providence and the Wyoming Valley.
 Allegheny also briefly operated Douglas DC-9-10 aircraft.