Two of the three remaining corridors in Delhi Metro's Phase-IV project were in advanced stages of approval. The authorities were also considering extending the third line to Kundli in Haryana. There was a plan to extend the proposed Tughalakabad-Aerocity (Silver Line) to Delhi Airport Terminal 1D on the Magenta Line. In March 2019, the Union Cabinet had approved three out of the six corridors of Delhi Metro's Phase-IV, which was set to enhance connectivity in the national capital. The three remaining proposed corridors, namely Rithala-Bawana-Narela, Inderlok-Indraprastha, and Lajpat Nagar-Saket G Block, had not yet received approval. Jaideep, Officer on Special Duty (Urban Transport) at the Ministry of Housing and Urban Affairs, mentioned to reporters that two of these remaining corridors under the Phase-IV project were in advanced stages of approval. Discussions were in progress with the Delhi Metro Rail Corporation (DMRC) about extending the Rithala-Bawana-Narela corridor to Kundli in Haryana, as per sources. If this extension received approval, it would mark Delhi Metro's fourth expansion into Haryana, following the Yellow Line (Gurugram), Violet Line (Faridabad), and Green Line (Bahadurgarh). This corridor was planned as an extension of the existing Shaheed Sthal-Rithala corridor of the Red Line. Interestingly, this could be Delhi Metro's first corridor connecting Haryana and Uttar Pradesh via Delhi, with the Shaheed Sthal metro station located in Ghaziabad, Uttar Pradesh.