Part ONE of the BFA Pathfinder achievement:
Look at da places!!
Quest in da places!!
Help da battle peoples!!
Make friends that REALLY Like you in da places!!
This looks a lot like Pathfinder Part One for Legion so be ready to explore and follow story lines in the various zones to finish the required chapters. As we learned with Legion, getting through the chapters in Legion pretty much got you to the required rep for the achievement (except Suramar the bastards).
Flying via Pathfinder achievements and unlocking it for your ACCOUNT rather than just paying per character to get flying is the new format. Complaining about it anywhere outside of the official WOW Dev forums does nothing to change that. Kick back and try to appreciate and enjoy the content, landscapes, and stories we are all traveling through together. The Devs are not out to get you. They go to work every day, just like you, and try to create something fun, interesting, and challenging for us to do. Let’s appreciate and enjoy that in a positive way.