Why would you FLY super sonic over a city

From the Times Of India, i read it and it made me laugh, but also wonder why the mig-21 went super sonic over a populated area.

Could it be some thing they noted near the border? or would it just be a fun thing to do? or testing of a upgraded Mig. or more like a publicity stunt to show they are still flyable?

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http://timesofindia.indiatimes.com/cms.dll/html/uncomp/articleshow?msid=195282

AHMEDABAD: The ‘blasts’ being reported from the city and other parts of the state were due to the ‘sonic boom’ caused by low flying of fighter plane, Indian Air Force sources said here on Monday.

The ‘sonic boom’ caused by a low flying MIG-21 fighter jet had caused the ‘blast’ like noises heard in several parts of Gujarat this morning, IAF spokesperson T K Singha told PTI.

It was a ‘planned profile’ by the IAF and there was no reason for panic, he added.

Singha said, “One MIG-21 fighter jet of the IAF was conducting a planned profile low flight from one of the bases at South West Air command (SWAC), at 13 km above sea level