Bharti Airtel is in talks to buy Vodafone Group's 21.05% stake in Indus Towers, which could potentially give India's second ranked telco a controlling interest, said two people aware of the matter. If Vodafone Plc sells its Indus stake to Airtel, it could infuse some of the proceeds into Vodafone Idea, its cash-strapped, local telecom venture with the Aditya Birla Group, industry experts said.