Army and IAF agencies monitoring movement of Pakistan aircraft reveal that till date this year, there have been about 60 reported incidents of breach of the `Air Agreement' signed by the Indian and Pakistani government a couple of years ago.

As per the terms of the agreement, no military aircraft or unscheduled civilian flights are to approach the restricted airspace over the IB. This airspace, akin to no-man's land on the ground, extends atleast 1,000 metres on either side of the demarcated IB and is out of bounds for all aircraft except trans-border flights.

Military sources say that this year, about 264 Pakistani aircraft, both combat as well as non-combat types, were observed in close vicinity of the IB.

The number of violations show that on an average, there are eight reported intrusions into the prohibited air-zone. Theseflights are observed and reported by BSF personnel manning pickets along the IB or by Army troops where their deployment is imperative. The Amritsar Sector, having the highest reported number of sorties and breaches, was particularly ``hot'' when a lot of work was being done on bunds near Ranian during flood control measures. Bunds also form important defences.

The Dera Baba Nanak Sector along the Ravi, with its network of ditch-cum-bund defence system has also remained active.

As per procedure, details about the number and type of aircraft sighted, their flight configuration and time of flight are passed on to the nearest Army division headquarters, which in turn directly intimates Army Headquartes along with the Command Headquarters.

The Army Headquarters intimates the Ministry of Defence and a ``protest'' is lodged through the embassy of the concerned country by the Ministry of External Affairs. Though no `scramble' of interceptors by the IAF in such cases had been reported, sources say that anydecision by ground forces to shoot down hostile aircraft would have to be taken on the spur of the moment, after determining the threat it poses. There have been instances of hostile aircraft coming right over the IB.

The issue of airspace violation has also repeatedly been raised and discussed during operational conferences and tactical briefings at the highest level and concerned has also been voiced at their frequency.

The only known instance of a infiltrating Pakistan aircraft being shot down was in 1996, when a Remotely Piloted Vehicle was downed in Kutch. Military sources say that though the breach may be inadvertent at times, there is a possibility of such aircraft involved in mapping out local defences.

``Their purpose could be a visual, first hand appraisal of our defences by commanders, judging the strength and layout of border out-posts as well as getting the lay of the land,'' an intelligence officer commented. Carrying photographic and survey equipment by these aircraft, particularlychoppers and transport aircraft, is not ruled out.

Helicopters of the Pakistan Army Aviation Wing, headquartered at Dhanval near Rawalpindi with detatchements attached with all major airbases for liason and search and rescue roles are also known to fly in close viciinity of the IB.

Another reason for flying in close proximity to Indian positions is for new pilots getting themselves familiar with the topography of the area. Possible errors in navigation during training exercises are also cited as a reason.

Sources say that some concessions in airspace restrictions have been allowed by both sides in the Northern Sector on account of the mountainous terrain. ``But they are trying to take advantage of these concessions in other sectors too,'' an officer commented.

Pakistan does not possess any strategic reconnaissance capability, for which it depends on inputs from China and the US. Though the No 5 Squadron equipped with 13 Mirage-IIIRD carries out tactical reconnaissance sorties from its base atSargodha, experts say that for border observations it flies atleast two-three kilometers behind the IB, using its `sideways' looking camera for photography.

Though there have been no known instances of the Mirage infiltrating Indian airspace, there were unconfirmed reports sometime back of the more advanced F-16s carrying reconnaissance pods and electronic radar jamming equipment entering Indian airspace.