Question: William Thomas Seawell was the head of what company that was the largest international airport carrier until 1991?

Context paragraphs:
William Seawell: William Thomas Seawell (January 27, 1918 – May 20, 2005) was a Brigadier General in the United States Air Force and former head of Pan Am.

AirAsia: AirAsia Berhad () is a Malaysian low-cost airline headquartered near Kuala Lumpur, Malaysia.  It is the largest airline in Malaysia by fleet size and destinations.  AirAsia Group operates scheduled domestic and international flights to more than 165 destinations spanning 25 countries.  Its main hub is klia2, the low-cost carrier terminal at Kuala Lumpur International Airport (KLIA) in Sepang, Selangor, Malaysia.  Its affiliate airlines Thai AirAsia, Indonesia AirAsia, Philippines AirAsia, and AirAsia India have hubs in Don Mueang International Airport, Soekarno–Hatta International Airport, Ninoy Aquino International Airport, and Kempegowda International Airport respectively, while its sister airline, AirAsia X, focuses on long-haul routes.  AirAsia's registered office is in Petaling Jaya, Selangor while its head office is at Kuala Lumpur International Airport.

Ministro Pistarini International Airport: Ministro Pistarini International Airport (Spanish: "Aeropuerto Internacional Ministro Pistarini" ) (IATA: EZE, ICAO: SAEZ) , known as Ezeiza International Airport owing to its location in the Ezeiza Partido in Greater Buenos Aires, is an international airport 22 km south-southwest of the Autonomous City of Buenos Aires, the capital city of Argentina.  It is the country's largest international airport by number of passengers handled—85% of international traffic—and is a hub for international flights of Aerolíneas Argentinas and LATAM Argentina.  Aerolineas Argentinas and its subsidiary Austral Lineas Aereas do operate limited domestic or "cabotaje" air service from Pistarini Airport as well.  Covering 3,475 hectares (13.42 sq mi; 8,590 acres), the airport serves Buenos Aires and its metropolitan area.  It has been operated by "Aeropuertos Argentina 2000 S.A." since 1998.

Sihanoukville International Airport: Sihanouk International Airport (formerly Sihanoukville International Airport) (IATA: KOS, ICAO: VDSV) (Khmer: អាកាសយានដ្ឋានអន្តរជាតិក្រុងព្រះសីហនុ French: "Aéroport International de Sihanouk" ), located 20 km east of Sihanoukville in Preah Sihanouk Province, is Cambodia's third largest international airport.  The airport is also known as Kaong Kang Airport (Kaong Kang, កោងកាង = mangrove).  The IATA code KOS is derived from Sihanoukville's alternative name "Kompong Som".

O. R. Tambo International Airport: O. R. Tambo International Airport (IATA: JNB, ICAO: FAOR) (ORTIA) is a major international airport in Kempton Park, Ekurhuleni, Gauteng, South Africa, near the city of Johannesburg and, to a lesser extent, the executive capital Pretoria.  It serves as the primary airport for domestic and international travel to/from South Africa and is Africa's busiest airport with a capacity to handle up to 28 million passengers annually with non-stop flights to all continents except Antarctica.  The airport is the hub of South Africa's largest international and domestic carrier, South African Airways (SAA), and a number of smaller local airlines.  The airport handled a total of over 20 million passengers in 2016.

Air Wisconsin: Air Wisconsin Airlines is a regional airline based at Appleton International Airport in the town of Greenville, Wisconsin, United States, near Appleton.  Air Wisconsin is the largest privately held regional airline in the United States.  It currently operates regional jet flights as American Eagle under contract to American Airlines via a code sharing agreement, serving cities in the U.S. and Canada with hubs at Boston Logan International Airport (BOS), Charlotte Douglas International Airport (CLT), Philadelphia International Airport (PHL) and Ronald Reagan Washington National Airport (DCA) .  Air Wisconsin previously operated United Express service on behalf of United Airlines followed by US Airways Express service on behalf of US Airways prior to becoming an American Eagle regional air carrier.  The company has announced it will once again partner with United Airlines as a United Express code sharing air carrier with primary hubs to be located at Chicago O'Hare International Airport (ORD) and Washington Dulles International Airport (IAD) beginning in September 2017 and will be "exclusively operating" as United Express by March 2018.

Air India: Air India is the flag carrier airline of India.  It is owned by Air India Limited, a government-owned enterprise, and operates a fleet of Airbus and Boeing aircraft serving 90 domestic and international destinations.  The airline has its hub at Indira Gandhi International Airport, New Delhi, alongside several focus cities across India.  Air India is the largest international carrier out of India with an 18.6% market share.  Over 60 international destinations are served by Air India across four continents.  Additionally, the carrier is the third largest domestic airline in India in terms of passengers carried (after IndiGo and Jet Airways) with a market share of 13.5% as of July 2017.  The airline became the 27th member of Star Alliance on 11 July 2014.

Grantley Adams International Airport: Grantley Adams International Airport (GAIA) (IATA: BGI, ICAO: TBPB) is the international airport of Barbados, located in Seawell, Christ Church.  It is the only designated port of entry for persons arriving and departing by air in Barbados and operates as a major gateway to the Eastern Caribbean.  The airport has direct service to destinations in the United States, Canada, Central America and Europe and serves as the second hub for LIAT.  In 2016, the airport was the 8th busiest airport in the Caribbean region; and the third busiest airport in the Lesser Antilles; after Queen Beatrix International Airport located in Aruba, and Pointe-à-Pitre International Airport located in the Republic of France within the island of Guadeloupe.  GAIA, also remains an important air-link for cruise ship passengers departing and arriving at the Port of Bridgetown, and a base of operations for the Regional Security System (RSS), and the Regional (Caribbean) Police Training Centre.

Turkmenbashi International Airport: Türkmenbaşy International Airport (IATA: KRW, ICAO: UTAK) , also known as Krasnovodsk Airport, is the second largest international airport in Turkmenistan.  It is located in city Türkmenbaşy (Krasnovodsk).  The airport opened in 1959.  Flights depart for Ashgabat (Ashgabat Airport), Daşoguz (Daşoguz Airport) and Istanbul (Atatürk International Airport).  Founded in 1959.

Pan American World Airways: Pan American World Airways, known from its founding until 1950 as Pan American Airways and commonly known as Pan Am, was the principal and largest international air carrier in the United States from 1927 until its collapse on December 4, 1991.  Founded in 1927 as a scheduled air mail and passenger service operating between Key West, Florida, and Havana, Cuba, the airline became a major company credited with many innovations that shaped the international airline industry, including the widespread use of jet aircraft, jumbo jets, and computerized reservation systems.  It was also a founding member of the International Air Transport Association (IATA), the global airline industry association.  Identified by its blue globe logo ("The Blue Meatball"), the use of the word "Clipper" in aircraft names and call signs, and the white pilot uniform caps, the airline was a cultural icon of the 20th century.  In an era dominated by flag carriers that were wholly or majority government-owned, it was also the unofficial overseas flag carrier of the United States.  During most of the jet era, Pan Am's flagship terminal was the Worldport located at John F. Kennedy International Airport in New York City.

Supporting paragraphs: William Seawell Pan American World Airways
Answer: Pan American World Airways