AFAIK, there are two runways at Islamabad airport-- well basically just one but you can approach it from different sides which have different labels.
Runway 30, which is normally used, has ILS but the other approach, namely runway 12, does not have ILS (instrument landing system). The plane could not land on runway 30 for some reason (high winds?) and had to land on runway 12 i.e. same runway but other side. But this does not have ILS system. So the usual procedure is to approach runway 30, then at a certain point make an elongated semi-circle (actually more rectangular in nature) and land on the other runway using visual approach (VOR) since you have the runway in sight.
The unfortunate flight made an approach to runway 30 as required, broke-away from the approach when directed to do so and made a 90° turn but failed to turn left again and went directly into the hills. For whatever reason, no one knows so far.
So its the opposite. He approach the runway with the instruments but was required to land from the other side that has no equipment. Its standard practice and practiced quite often throughout the world where airports have ILS on only one approach.
P.S. If this is correct, then there is no indication thats got anything to do with Kahuta or tarbela or whatever. Besides, the pilot maintained communication with ATC till about 2 mins before impact and nothing suspicious was reported. Also nobody saw any damage or fire to indicate the plane was shot at nor did anyone hear anti aircraft guns. Similarly, no mayday calls were received to indicate any trouble within the cockpit.
