Students from the University of Montreal, the main source of Blue Line riders, obtained an extension of the closing time to 11:10 pm and then 12:15 am in 2002.

[15] The provincial government announced that the extension would proceed and committed $38.8 million to set up a project office tasked with preparing detailed financial and technical plans within two years.

The successor Liberal government had expressed interest in extending mass transit to Montréal–Trudeau International Airport and implementing a light rail line on the new Champlain Bridge under construction.

[17] On 9 April 2018, premier of Quebec Philippe Couillard and Prime Minister Justin Trudeau announced their commitment to fund and complete the extension, then planned to open in 2026.

[19] The 6-kilometre (3.7 mi) extension was set to include five new stations, two bus terminals, a pedestrian tunnel connecting to the Pie-IX BRT and a new park-and-ride.

[23] Procurement work to build the tunnels and stations began in the fourth quarter of 2022, and major construction will follow after contractors are appointed.

[24][20] In January 2023, the STM announced that five Quebec artists – Jocelyne Alloucherie, Ludovic Boney, Nadia Myre, Alain Paiement and Marc Séguin – had been selected to create public art at each of the new stations.

[25] In September 2023, construction tenders for the tunnel boring machine were called and an announcement was made that the opening date would be delayed to 2031.

[26] The original intent for the Blue Line was that it would extend southwest from Snowdon to serve Notre-Dame-de-Grâce, Hampstead, Montreal West and Ville Saint-Pierre.

[4][27] Snowdon station was constructed with a cross-platform interchange to allow easy access to Orange line trains heading downtown.

[28] The preceding MR-63 train type spent its final day in revenue service on the Blue Line but otherwise rarely appeared on it.