Any time you have a plane crash with military members completing exercises, it is likely that it resulted from pilot error. Of course, there are other possibilities, such as the air place malfunctioning. An inquiry is usually made after such a crash and eventually a final report will be released. This usually states the cause.
Pilot error is the more likely reason for the crash. The Indian Air Force inspects and maintains aircraft with the specific goal of ensuring the aircraft is fit for operation. Pilots are highly trained individuals, but there are so many possible errors they can make. They could fall asleep, make an incorrect instrument reading. Pilots have to make many decisions. Each decision could be incorrect and possibly endanger everyone aboard the aircraft. We hope that any pilot will always make the right call, but the truth is that pilot error is always a likely possibility in a plane crash.
Humans make many errors everyday - just a simple error can cause a crash in minutes. Although he is unlikely to do this on purpose, the probability of him causing the crash suggests it was a pilot error. However, it must be examined to be confirmed, as it could also be due to mechanical or electronic error.
Was the crash a result of pilot error? Anything is possible but an investigation would need to be conducted before any speculation can be addressed. Has the black box from the plane been found? There are more questions to be answered before too many answers can be given. Has an investigation been performed?