Question: Hi Fly Malta is a subsidiary of a charter airline headquartered in what city?
Context: Euralair was a charter airline based in France.  Euralair was founded in 1964 as an air-taxi and executive charter company.  In 1966 it became charter airline and operated its first charter flights in 1968 when it received the first Fokker F-27 (F-BRHL) on November 11, 1968 and the second (F-BRQL) on October 15, 1969; the last one sold to the Swiss company Belair (as HB-AAZ) in June 1973.  In order to develop its charter activity, on November 1971 Euralair bought from Austrian Airline the first Sud Aviation Caravelle VIR (F-BSEL) and in 1973 the second (F-BTDL). Hi Fly is a Portuguese charter airline headquartered in Lisbon. Hi Fly Malta is a Maltese charter airline based at Malta International Airport and a subsidiary of the Portuguese Hi Fly. Trade Air d.o.o. is a Croatian passenger and cargo charter airline headquartered in Zagreb and based at Zagreb Airport.  The company is registered as an airline whose main activities are passenger charter flights and cargo operations, organized either on charter chain flights or "ad hoc" flights.  Trade Air also specialises in the transportation of dangerous goods. Canada 3000 Inc. was a Canadian discount charter airline offering domestic and international flights.  It was the largest charter airline in the world at the time of its operation, with over 90 destinations worldwide, although it changed to scheduled service in 2000 after the Canadian Airlines and Air Canada merger.  Canada 3000 competed with Air Canada, WestJet, and fellow charter airline Air Transat.  In November 2001, the airline went out of business after a sharp decline in revenues following the September 11, 2001, terrorist attacks in the United States.  There have been several attempts to restart the airline since then.  The airline was headquartered in Etobicoke in the west-end of Toronto, Ontario. Sun America, Inc., d/b/a JetAmerica, was a proposed American low-cost scheduled public charter airline headquartered in unincorporated Pinellas County, Florida.  On March 10, 2009, the airline announced a number of public scheduled charter flights from underutilized airports to Newark and Minneapolis–St. Paul using a Miami Air International Boeing 737-800 to begin on June 30, 2009.  On May 27, 2009, the airline held its first press conference at Toledo Express Airport, Ohio, announcing its first focus city and the start of flight operations on July 13, 2009.  The airline announced the station markets of Lansing, Michigan; Melbourne, Florida; Minneapolis, Minnesota; Newark, New Jersey; South Bend, Indiana; and Toledo, Ohio.  The airline also publicly stated it was evaluating service to Baltimore, Maryland; Charleston, West Virginia Chicago Midway, Illinois; Rockford, Illinois; Cincinnati, Columbus, and Dayton, Ohio; Greensboro, North Carolina; Hartford, Connecticut; Pittsburgh, Pennsylvania; and Clearwater, Florida.  The airline later delayed the start of service to August 14, 2009.  However, JetAmerica did not begin service as it was unable to finalize slots at Newark. Strategic Airlines SA, known as Strategic Airlines Luxembourg or Strategic Airlines, was a charter airline headquartered in Luxembourg that operated flights out of the United Kingdom.  The airline had bases at Manchester, Birmingham and London-Gatwick offering holiday charter flights for mainly tour operators. TUI fly Netherlands, legally incorporated as "TUI Airlines Netherlands" (formerly branded as "Arkefly" and "Arke"), is a Dutch charter airline headquartered in Schiphol-Rijk on the grounds of Amsterdam Airport Schiphol in Haarlemmermeer, Netherlands.  It is the charter carrier of the Dutch arm of the German travel conglomerate TUI Group and its main base is Schiphol Airport. TUI fly Nordic is a charter airline headquartered in Stockholm, Sweden and is a part of the TUI Group.  It operates short, medium and long-haul flights to leisure destinations from several airports in the Nordic countries, on behalf of the tour operators TUI Danmark (Denmark), TUI Suomi (Finland), TUI Norge (Norway) and TUI Sverige (Sweden).  In 2016, the airline carried approximately 1,500,000 passengers. Lauda Air Luftfahrt GmbH, branded as Lauda Air, was an Austrian airline headquartered at Vienna International Airport in Schwechat.  It was owned by Niki Lauda during much of its existence, later becoming a charter airline subsidiary for leisure operations of Austrian Airlines.  On 6 April 2013, Lauda Air ceased to exist and was replaced by "Austrian myHoliday", a new brand name that is used for flights and leisure offers provided by Austrian Airlines.
Answer: Lisbon