Airports Authority of India currently provides several systems to support en-route and terminal area navigation, including non-precision approach. These include VOR with associated DME, NDBand GPS.
The operational benefits of GPS/GAGAN, especially increased routing flexibility and many more precision approaches, will motivate most operators of aircraft used extensively for IFR operations to equip with GPS/GAGAN in the five to six year period following the availability of services. At that point, the current ground based systems - VOR, DME, and ILS - will become back-up systems for these operators. Since most aircraft will be navigating using GPS/GAGAN, substantial reductions can then be made in the number of VOR/DME and ILS ground facilities. Maintaining the current VOR/DME system is expensive, thus, there is a considerable financial incentive to reduce the number of VOR/DME. As soon as GPS/GAGAN avionics are available, operators are anticipated to begin equipping with it to achieve the associated operational benefits and convenience.