opening date to late 2005. June 2006: City council pledges to do its best effort to complete phase 1 by the end of the year. December 2006: The opening date is pushed to January 2007. January 2007: Due to delays in completing from infrastructure, the opening date is pushed by one month to February 2007. February 3, 2007: Phase one, renamed "Eje Sur" (South line), begins operating in the city. August 14, 2010: The second phase opens, renamed "Eje central" also known as "Corredor Central" (Central line, or also known as Central corridor). December 2012: A short line begins to operate in the Historic Downtown aka "Centro Historico" April 2014: A new line begins to operate to serve Zone 18 from the Atlantida neighbourhood to the Downtown core. 2014: Construction begins for the northern line, later renamed line 6 after the Zone in which it terminates from the downtown core. April 2015: Line 6 (Eje Norte), begins service. January 2016: A new short line opens to serve the Racecourse neighbourhood to the downtown core 2016: All lines were renamed after the zones they operate in or serve. Eje Sur was renamed Line 12 as it mainly operates in zone 12, Corredor Central was renamed Line 13 as it connects Zone 13 with the Downtown Core, Cnetro Historico was renamed Line 1 as it serves the Zone 1 Downtown, Eje Norte was renamed Line 6 as it terminates in Zone 6, Eje Nor-oriente is renamed Line 18 as it terminates in Zone 18, Hipodromo was renamed Line 2 as it serves Zone 2. 2017: Line 21 begins operating as a pilot project to improve transportation to and from the USAC University campus. It had not yet been changed to a permanent route but is marked on the map as the pink line. 2019: Line 7 begins to operate with some stations still under construction. Line 21 is made permanent. 2020: All Line 7 stations are open to the public. In early 2020, the new mayor announces plans to phase out cash-fares. 2021: New payment card "Tarjeta Ciudadana" becomes the default payment method, and cash payments are no longer accepted. 2023: Several service changes were made to the network, including the official removal of all direct interchanges, with the exception of those on Lines 6 & 18 and Lines 1 & 2, addition of new stations on Lines 1, 2, 12, 13,