New Delhi, Feb 06: The Indian Air Force (IAF), along with Civil Aviation authorities, maintains a close vigil over Indian skies during peacetime. The area of jurisdiction or the air defence zone (ADZ) is 12 nautical miles from the coastline of the main peninsula and a perimeter of a similar distance around the island territories. The ADZ is protected by multi-layered sensor systems with different but complementary capabilities. Though air power is primarily offensive in nature, the IAF's major role during peacetime is deterrence. This is primarily maintained by surveillance through various forms — air borne and ground, both static and mobile.