Luftwaffe Pilot/Aircrew training routes and stages

Can anyone please go through the steps and different routes that a typical Luftwaffe pilot and a Luftwaffe Aircrew member could take? I understand their was different routes but what confuses me is how some of them are ranked. Some pilots and even Observers were commissioned officers, and some pilots and aircrew were non-commissioned officers. How was this decided? Would they go to officer candidate school or NCO'S school after basic training in the Flieger-Ersatz-Abteilung? Was it common for an aircrew member, or even a pilot to rise through the ranks from a flieger or gefreiter to a nco/commissioned officer? Would they go to their training specialization schools after nco school or officer candidate school? I do know training, especially late in the war, varied but I can't find much details on the training of Luftwaffe members and any information would be greatly appreciated!