Expansion of the present aiport
According to Wikipedia, "An integrated simulator will be installed at Chennai Airport, which will be the first of its kind in the country, at a cost of ₹200 million. The equipment will be set up at the Air Traffic Services complex. In January 2018, a satellite terminal near the second runway was planned to be built in 3 years. A 1.5 km tunnel to connect the satellite terminal with the main buildings has been planned at a cost of ₹7,000 million. This tunnel will run at a depth of 10.5 feet below the ground. Following the ₹23,000 million phase I expansion that began in 2007 and completed in 2013, the phase II expansion comes at a cost of ₹25,870 million is expected to begin in 2018, aimed to be completed in 42 months by September 2021. This will expand the area to 160,000 m2, with a capacity of 35 million passengers, up from the existing capacity of 18 million. With the completion, the new building will serve as the sole integrated terminal alongside the existing newer domestic and international terminals. As of July 2018, the AAI had acquired 130 acres of land for the expansion of the present airport, and acquisition of another 101 acres of land is in progress.[148] Construction of the new integrated terminal is under progress and completion is expected by December 2022, which was delayed due to the COVID-19 pandemic. Commission will be done in two phases, the primary at June 2021. Automatic boarding, additional food courts, expansive baggage claim and arrival area, extra greenery, and state-of-the-art architecture designs are features of the new terminal. Officials say with this they will be able to surpass the present service rank of the airport, which was lacked in poor maintenance, both nationally and internationally. The airport lagged in star ratings a lot behind other comparative major airports like Bangalore, Kolkata, and Hyderabad in Skytrax Airport Awards and other reviews due to its insufficient terminal space and sanitization facilities at restrooms."
Second Airport
Currently there are plans of building a greenfield airport within Chennai. It is said that this new construction will take place in 2 phases. The new greenfield airport is expected to handle approximately 40 million passengers every year. Please note that this information is based off on Tamil Nadu's vision 2023 document.