Defence Minister Manohar Parrikar today said, India must rethink its submarine building plan and look for greater numbers than the existing plan of making 24 submarines.<br/><br/>Referring to the existing 30-year submarine building plan that envisages construction of 24 submarines–both nuclear and conventional, Mr Parrikar said India needed a longer plan till 2050. The existing plan ends in 2030 and the first submarine under it, the Kalvari, will be commissioned in January 2017.<br/><br/>Speaking on the sidelines of a function in New Delhi, Mr Parrikar said to maintain and sustain the knowledge in submarine making, India needed a longer plan.<br/><br/>Navy chief Sunil Lanba said the submarine design is an area that posed considerable challenge for indigenous development.