If their target were within fuel range, which India probably is, the attack would have taken place already.
If this is truly a planned event, it is more complicated than crashing an airplane into a building...unless that building is far far away and requires refueling and other preparations.
So who was on board?
Maybe nuclear scientists?
Government couriers carrying secret documents?
Engineers working on secret weapons?
If it is a highjacking, these are questions that need to be examined.
Or the crew went absolutely mad and there is no explanation...but that would have ended in a fireball long ago.
Most likely this is al Qaeda or an al Qaeda-allied terrorist cell.
The other aircraft plots like 9/11, the shoe bomber, the underwear bomber, were al Qaeda-planned missions.
The cell members might be any nationality, Iranian or Egyptian or Malaysian or what have you, and they perform whatever mission they are given by the leadership. And the al Qaeda leadership is closely tied to elements in Pakistan, as even bin Laden himself was living in a compound in a Pakistani military city.