King Khalid Military City (KKMC) (Arabic: مدينة الملك خالد العسكرية‎ ‎ ; transliterated: "Medinat Al-Malek Khaled Al-Askariyah") is a special city in northeastern Saudi Arabia and about 60 km south of Hafar Al-Batin City, designed and built by the Middle East Division, a unit of the United States Army Corps of Engineers, in the 1970s and 1980s.
 The consultants were Brown, Daltas, and Associates in Cambridge, Massachusetts.
 The city was built to provide lodging for several brigades of Saudi troops, with a design population of 65,000 people.
HOK, formerly Hellmuth, Obata + Kassabaum, is an American worldwide design, architecture, engineering and urban planning firm.
Thumamah Airport (ICAO: OETH) is an airport located near Ath Thumamah in Saudi Arabia.
 It is located about 28.9 km (18 mi) north of King Khalid International Airport.
King Khaled Military City Airport (Arabic: مطار مدينة الملك خالد العسكرية‎ ‎ , IATA: KMC, ICAO: OEKK ) is an airport in King Khalid Military City, Eastern Province, Saudi Arabia.
 It is located 70 km southwest of Hafar Al-Batin.
King Khalid International Airport (Arabic: مطار الملك خالد الدولي; "Maṭār al-Malik Khālid al-Duwaliyy", IATA: RUH, ICAO: OERK ) is located 35 km north of Riyadh, Saudi Arabia, designed by the architectural firm HOK, and Arabian Bechtel Company Limited served as the Construction Manager on behalf of the Saudi government.
Saudia (Arabic: السعودية‎ ‎ "as-Suʿūdiyyah "), also known as Saudi Arabian Airlines (الخطوط الجوية العربية السعودية), is the national carrier airline of Saudi Arabia, based in Jeddah.
 The airline's main operational base is at King Abdulaziz International Airport in Jeddah.
 King Khalid International Airport in Riyadh and King Fahd International Airport in Dammam are secondary hubs.
 The new Dammam airport was opened for commercial use on 28 November 1999.
 Dhahran International Airport in use until then, has reverted to being used as a military base.
 The airline is the third largest in the Middle East in terms of revenue, behind Emirates and Qatar Airways.
 It operates domestic and international scheduled flights to over 120 destinations in the Middle East, Africa, Asia, Europe and North America.
 Domestic and international charter flights are operated, mostly during the Ramadan and the Hajj season.
 Saudia is a member of the Arab Air Carriers Organization and joined the SkyTeam airline alliance on 29 May 2012.
GoJet Airlines LLC is a company headquartered in Bridgeton, Missouri, United States.
 Wholly owned by Trans States Holdings, it has 1670 employees.
 It operates commuter feeder services under the United Express and Delta Connection names.
 Go Jet Airlines has crew bases at Lambert-Saint Louis International Airport, O'Hare International Airport, Denver International Airport, and Raleigh-Durham International Airport.
 Flights are currently operated out of United's hubs at O'Hare International Airport and Denver International Airport, as well as Lambert-Saint Louis International Airport.
 GoJet's Delta Connection flights currently operate out of Lambert-Saint Louis International Airport , Detroit Metropolitan Airport and Raleigh-Durham International Airport.
 Its call sign "Lindbergh" is named after aviation pioneer Charles Lindbergh, who flew the "Spirit of St. Louis" solo across the Atlantic Ocean in 1927, the first person to do so.
Triangular Pyramid Factory is a metal fabrication and production company based in Riyadh, Saudi Arabia.
 The company was established in 2002 through Saudi Arabian General Investment Authority, as part of measures geared towards formalizing the process of economic liberalization.
 Triangular Pyramid factory is one of the largest manufacturer and supplier of carbon steel, aluminium and stainless steel in Arabian peninsula.
 The company has been involved in the construction of King Khalid International Airport and Marriott Courtyard, Riyadh.
Kayala Airline (previously called Al Khayala) was an airline based in Jeddah, Saudi Arabia.
 Kayala was a privately owned premium class airline operating domestic and international scheduled as well as charter services.
 Its main base was King Abdulaziz International Airport, Jeddah, with a hub at King Khalid International Airport, Riyadh.
Lufthansa Cargo Flight 8460 was an international cargo flight that on 27 July 2010 (15 Sha'aban 1431 H), crashed upon landing at King Khalid International Airport, Riyadh, Saudi Arabia.

Question: What is the nationality of the company that designed the King Khalid International Airport?
Answer: American