Question: At what airline's largest hub will the Cotton Belt Rail Line have a major terminal? 

Context paragraphs:
Cotton Belt Rail Historical Society: The Cotton Belt Rail Historical Society, Inc. (CBRHS) is a non-profit organization that is dedicated to the restoration and preservation of the history of the St. Louis Southwestern Railway (SSW), commonly referred to as the "Cotton Belt".

Lone Star (St. Louis Southwestern train): The Lone Star was a passenger train operated by St. Louis Southwestern Railway (Cotton Belt) between Memphis, and Dallas, with through connections via Cotton Belt parent, Southern Pacific, for San Antonio, El Paso, and ultimately Los Angeles.  There were also through cars operating between Memphis, Lewisville and Shreveport.  At various times during the train's operation, connecting services were also provided from Brinkley to St. Louis.  The train was discontinued on November 1, 1952, as a part of extensive passenger train restructuring by St. Louis Southwestern.  The "Lone Star" was replaced by trains number 107 and 108 which connected with the Cotton Belt mainline at Mount Pleasant, Texas.

CityLine/Bush station: CityLine/Bush station (formerly Bush Turnpike station) is a DART Light Rail station in Richardson, Texas.  It is located on the President George Bush Turnpike near US 75 (Central Expressway).  It opened on December 9, 2002 as a station on the Red Line , serving the area around Collin Creek Mall.  The Orange Line was added in 2010.  The station is planned to be an intersection between those lines and the future Cotton Belt Rail Line.

Addison Transit Center: Addison Transit Center is a bus-only station located along Quorum Drive and Addison Road in Addison, Texas (USA).  The station opened in 1999.  This transit center will become a future rail station on the Cotton Belt Rail Line as part of DART's 2030 Transit System Plan.

TEXRail: TEXRail (also known as the Tarrant Express Railway, formerly known as the Southwest-to-Northeast Rail Corridor) is an under-construction commuter rail line in Tarrant County, Texas, United States that will provide service from southwest Fort Worth to DFW International Airport via Grapevine and other Tarrant County communities.  It is being constructed by the Fort Worth Transportation Authority ("The T") and is scheduled to open in 2018.  The new line is expected to cost $330 million, of which 10 percent would be Grapevine's share.  This segment of the Cotton Belt Rail Line will be operated independent of the other two segments, as it is being built by the T, instead of DART, who will be building the other segments.

Alexander, Texas: Alexander is an unincorporated community located in southern Erath County in Central Texas.  Alexander is in the southern part of the county along Texas State Highway 6 and Fm-914.  The town was originally called: "Harper's Mill" when the Post Office was approved for operation around the 1870s.  The name was changed in the 1880s when the Texas Central line part of the historic Katy Railroad was built from east to west through the townsite on its way from the Waco area to Stamford with a branch to Cross Plains from the line at De Leon.  In 1907 the Stephenville North and South Texas Railway part of the Cotton Belt Route was constructed from north to south and crossed with the Katy's line in Alexander.  This made the town an important community for business in the area.  The Cotton Belt Route ran from Stephenville through to nearby Carlton.  On October 17, 1934 the Cotton Belt Route was abandoned from Stephenville to Hamilton.  The Katy Railroad remained through Alexander until its abandonment in the late 1960s.  The Alexander post office closed in 1970 and the population remained at a steady 40 from the 1970s through 2000.

12th Street station (DART): The 12th Street station is a potential future DART Light Rail station along the Cotton Belt Rail Line and the Red Line.  If constructed, the station will be located at 1116 12th Street in Plano, Texas.  The City of Plano recently bought a piece of land in anticipation of its construction.

Shiloh Road Station: The Shiloh Road Station will be a future station located in Plano, Texas on the proposed Cotton Belt Rail Line.  It is located near the corner of 14th Street and Shiloh Road.  The City of Plano bought land for the future station, if the line is built.  It will be the eastern terminal for the commuter line, unless the towns of Murphy, Texas and Wylie, Texas become member cities and allow for expansion.

Dallas/Fort Worth International Airport: Dallas/Fort Worth International Airport (IATA: DFW, ICAO: KDFW, FAA LID: DFW) is the primary international airport serving the Dallas–Fort Worth metroplex area in the U.S. state of Texas.  It is the largest hub for American Airlines, which is headquartered near the airport.  2016 was a record year for DFW, as the airport served 65,670,697 passengers.

Cotton Belt Rail Line: The Cotton Belt Rail Line is a planned 67.7 mi group of commuter rail lines in Tarrant, Dallas, Collin, and Rockwall Counties in the U.S. state of Texas.  The lines will provide service from Dallas's northeast suburbs to Southwest Fort Worth with a major terminal at the north end of Dallas/Fort Worth International Airport.  The project has been broken up into several lines under development by Dallas Area Rapid Transit and the Fort Worth Transportation Authority.

Supporting paragraphs: Cotton Belt Rail Line Dallas/Fort Worth International Airport
Answer: American Airlines