I've been doing some work regarding the analysis of boeing 737-300 fuel consumption in commercial flights, and how all of them fare with the fuel consumption standards, like fuel consumption rate at certain flight phases, and such, to like assess how efficient certain flights or routes are in their fuel consumptions
Been finding sources all over internet, but can't sure which one is kinda official and reliable.
So where exactly to look online? are there any documents that would contain such information that is reliable. or better, official?