The central government has proposed the development of six greenfield airports, one each in Chennai, Kolkata, Bagdogra, Pune, Varanasi and Nalanda, on a public-private partnership basis utilising the land pooling model for land acquisition. Under this model, the land owned by different individuals is pooled together and the owners get back a certain portion of the developed area valued higher than the original land. The Airports Authority of India (AAI) has appointed the Centre for Environmental Planning and Technology for studying this model. Further, the state governments have been tasked with identifying a minimum of 2,500 acres of land for the development of these airports. Post-identification, technical feasibility studies of the sites will be undertaken. Meanwhile, in a separate development, AAI is planning to spend Rs 180 billion over the next four years to expand its airports.