Can anyone reccomend the most reliable and precise website for retrieving on-time (and therefore including delays) stats for international sites.

I tried on the carriers web page, but it doesn't seem to be to comprehensive.
flightstats and flightaware seem to be ok, but then, how come they return totally different data for the very same flights?
which one should i refer to as the most correct? Am i missing something?any other suggestions?


Thank you in advance