Question:  MS "Freedom of the Seas" is a cruise ship operated by a cruise line operating how many ships?
Context: MS "Europa 2" is a cruise ship operated by Hapag-Lloyd Cruises, a German-based cruise line.  She entered service in May 2013, and is the highest rated cruise ship in the world according to the "Berlitz Guide to Cruising & Cruise Ships", replacing her fleetmate, MS "Europa" , which had held that distinction for more than a decade. Fiesta Marina Cruises was an experimental short-lived subsidiary cruise line of Carnival Cruise Lines.  The cruise line was marketed toward the Latin/Spanish-speaking population, residing in the United States and abroad.  The cruise line sailed out of San Juan, Puerto Rico and Caracas, Venezuela.  The cruise line operated only one ship, the "Fiesta Marina".  The ship was named in Miami, Florida on October 18, 1993.  The cruise line was a total marketing failure and was dissolved in September 1994.  The "Fiesta Marina" was sold to Epirotiki Cruises to sail as the "Olympic".  In 2007, the Carnival Corporation started a joint-partnership with the Orizonia Corporación to start a new cruise line called Iberocruceros.  Just like Fiesta Marina, the new cruise line was marketed toward the Latin/Spanish-speaking population.  The cruise line operated out of South America and Europe, independently from Carnival, but was managed by Costa Cruises.  Iberocruceros was closed in 2014 and its ships transferred to Costa or elsewhere. MS "Independence of the Seas" is a "Freedom"-class cruise ship operated by the Royal Caribbean cruise line that entered service in April 2008.  The 15-deck ship can accommodate 4,370 passengers and is served by 1,360 crew.  She was built in the Aker Finnyards Turku Shipyard, Finland, builder of "Freedom of the Seas "and "Liberty of the Seas", her sister ships of the "Freedom "class.  At 154,407 GT, she joined "Freedom of the Seas" and "Liberty of the Seas" as the largest cruise ships and passenger vessels yet built.  She is 1112 ft long, and typically cruises at 21.6 kn .  The vessel operates from Fort Lauderdale, Florida during the Fall and Winter months and Southampton, England during the Spring and Summer months. Imperial Majesty Cruise Line was a budget cruise line that had operated 2 and 3 day voyages out of Port Everglades, Florida to Nassau, Bahamas.  The company was founded in 1999.  The cruise line attracted both vacationers and vintage ship fans from around the world.  The cruise line's current operations ended on March 9, 2009, when the Regal Empress was retired.  In that same week, its operations were replaced by another cruise line operating for the same company that Imperial Majesty was part of. Majesty Cruise Line is a Norwegian cruise line probably known for owning the Norwegian Majesty from 1992 to 1997.  Majesty Cruise Line was a more upmarket brand created by Dolphin Cruise Line in 1993.  Their first ship, the Royal Majesty, was originally ordered by Birka Line for their 24-hour cruises out of Stockholm.  Following the bankruptcy of builders Wärtsilä, the contract was resold to Majesty Cruise Line and the vessel was completed as Caribbean cruise ship Royal Majesty in 1992.  She initially worked three- and four-night cruises out of Florida, but in 1995 opened a new summer Boston-Bermuda route, terminating at St George's rather than the usual Hamilton in Bermuda.  Royal Majesty returned to Florida in the winter.  In June 1995 she ran aground on Rose and Crown shoal of Nantucket Island, due to a combination of faulty GPS and inadequate watch being maintained.  Royal Majesty was 17 miles off course.  She remained aground for 24 hours before tugs towed her off.  In 1997, a second ship was added to the fleet, the Crown Majesty (previously Crown Dynasty).  For the 1997 season, she operated cruises which had already been arranged for Crown Dynasty, but at the end of that season both ships passed to Norwegian Cruise Line (NCL).  Royal Majesty was sold to NCL, being renamed Norwegian Majesty, and soon received a similar lengthening to Norwegian Wind/Dream.  Crown Majesty which had been chartered from Effjohn International, had her charter transferred to NCL. MS "Regal Empress was a cruise ship that recently operated for Imperial Majesty Cruise Line.  She was built in 1953 by Alexander Stephen & Sons at Glasgow, Scotland as the ocean liner SS "Olympia for the Greek Line.  Greek Line withdrew the "Olympia" from service in 1974.  Following an extended lay-up period and reconstruction into a diesel-engined Caribbean cruise ship, the ship re-emerged in 1983 as MS "Caribe I" for Commodore Cruise Line.  In 1993 she was sold to Regal Cruise Line and received her final name.  She operated for Imperial Majesty Cruise Line from 2003 until 2009.  The "Regal Empress" was also the last vintage passenger ship to regularly sail from the United States. RMS "Transvaal Castle was a British ocean liner built by John Brown & Company at Clydebank for the Union-Castle Line for their mail service between Southampton and Durban.  In 1966 she was sold to the South Africa-based Safmarine and renamed S.A. Vaal for further service on the same route.  Following cessation of the service between the UK and South Africa in 1977 the ship was sold to Carnival Cruise Line and rebuilt in Japan as the cruise ship SS "Festivale, re-entering service in 1978.  In 1996 she was sold to Dolphin Cruise Line and renamed IslandBreeze.  The vessel spent some of her time under Dolphin Cruise Line ownership on charter to Thomson Cruises.  In 1998 the ship was sold to Premier Cruise Line and renamed SS "Big Red Boat III.  Following the bankruptcy of Premier Cruise Line 2000, "Big Red Boat III" was laid up until 2003 when she was sold to the scrappers in Alang, India.  The ship became The Big Red Boat" for her final voyage to the scrapyard. Royal Caribbean International is a cruise line brand founded in Norway and based in Miami, Florida, United States.  It is owned by Royal Caribbean Cruises Ltd.  s of March 2017 , the line is operating 24 ships, has six additional ships on order, and controls 21.9 percent of the cruise market worldwide.  All ships under the Royal Caribbean International brand have names ending with "of the Seas" (e.g. "Empress of the Seas" ) a practice which began in 1991. MS "Freedom of the Seas" is a cruise ship operated by Royal Caribbean International.  It is the namesake of Royal Caribbean's "Freedom" class, and can accommodate 3,634 passengers and 1,300 crew on fifteen passenger decks.  "Freedom of the Seas" was the largest passenger ship ever built (by gross tonnage) from 2006 until construction of the Royal Caribbean International's "Oasis"-class ships in late 2009. Celestyal Crystal, previously Louis Cristal, is a cruise ship operated by the Cyprus-based Celestyal Cruises and previously Louis Cruise Lines, both in the Louis Group.  The ship was originally built as the cruiseferry MS "Viking Saga in 1980 at Wärtsilä Turku New Shipyard, Turku, Finland for Rederi Ab Sally.  In 1986 she was renamed MS "Sally Albatross, and rebuilt into a cruise ship the following year.  The ship was destroyed by a fire in 1990, and completely rebuilt at Finnyards, Rauma, Finland.  She was re-delivered in 1992, still named "Sally Albatross".  After partially sinking 1994 she was rebuilt at Industrie Navali Maccaniche Affini, La Spezia, Italy, re-entering service as MS "Leeward for Norwegian Cruise Line.  Subsequently she sailed as MS "SuperStar Taurus for Star Cruises, MS "Silja Opera for Silja Line and spent a year laid up as MS "Opera prior to entering service with her current owner in 2007.
Answer: 24