Spice Jet Airlines — Cancellation of flight and diversion of passengers

Address:

Hyderabad, Andhra Pradesh

My old parents were booked on Spicejet flight SG-872 from Kolkata to Hyderabad, on 11 Aug 2010.
After they checked in at Kolkata airport on schedule, they were suddenly informed that their flight to Hyderabad was terminated. They were then made to wait for an hour, and unceremoniously shepherded into a Mumbai bound flight. At the time they were supposed to land at Hyderabad, they were thus landing at Mumbai. They were made to wait for another 2 hours at Mumbai, before being put on a flight to Hyderabad.
Instead of reaching Hyderabad at 1800 hrs on 11 Aug 2010, they finally reached at 2330 hrs.
As a result they were greatly inconvenienced by Spicejet.
I now wish to know how to claim compensation from Spicejet for being more than 5 hours late in reaching Hyderabad.