A seven-layer security ring has been thrown around the VVIP enclosure on Rajpath from where Obama, President Pranab Mukherjee, Prime Narendra Modi and a host of other dignitaries witnessed the grand parade.
Central Delhi has turned into a virtual fortress with nearly 40,000 personnel drawn from Delhi Police and paramilitary forces guarding every nook and corner of the area.
More than 15,000 CCTV cameras installed have been relaying every movement live to a central control room where the footage has been monitored by a joint team of Delhi Police, US Secret Services and sleuths of central security agencies.
The three-km stretch of Rajpath has over 160 CCTV cameras - with one camera installed at every 18 metres.
Snipers and spotters of the National Security Guard (NSG) and Delhi Police have been deployed on all nearby high-rises which overlook Rajpath while dedicated radar monitored the air space.
Anti-aircraft guns have been put on standby to shoot down any aerial intrusion.
The Director General of Civil Aviation has issued a 'NOTAM' (Notice to Air Men) for diverting all flights flying over Delhi at the time of the parade.
Earlier, planes flying above 32,000 feet did not fall in the category of no-fly zone, but now the height has been raised to 35,000 feet, the sources said.
No plane will be flying within a radius of 400 km of Rajpath as against 300 km on earlier occasions, they said. This means airports adjoining Delhi like Jaipur, Agra and as far as Lucknow or Amritsar will not operate flights when the function will be on in the national capital.

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