Planning for the connection to the IND Queens Boulevard Line began in December 1990, with the final design contract awarded in December 1992. Two build alternatives were evaluated: a connection to the local tracks of the Queens Boulevard Line, and a connection to the local and express tracks. The goal of the project was to increase capacity on Queens Boulevard by 33% and to eliminate the dead-end terminal at 21st Street–Queensbridge. Bellmouths were constructed to allow for a future bypass line through Sunnyside Yard. The remaining section from 21st Street to the Queens Boulevard Line, which cost $645 million, began construction on September 22, 1994. The construction project involved a number of other elements, such as extending the lower level LIRR tunnel and widening the Queens Boulevard Line tunnel above. In December 2000, the 63rd Street Connector was opened for construction reroutes, and opened for off-peak reroutes on January 13, 2001. while signal work was performed in the 53rd Street Tunnel. Regular service was expected to begin by August or September of that year, but the September 11, 2001, terrorist attacks delayed the commencement of regular service. The connector came into regular use on December 16, 2001, with the start of V service in the 53rd Street Tunnel and the rerouting of F service at all times to 63rd Street.