The F major scale is the first in line in terms of keys with flats in them. It's the scale with one flat. It starts and ends on F and all the notes in between are white notes except for Bb. The key of F has Bb (B flat).
In terms of flat keys, the F major scale comes first. It is a one-flat scale. Except for Bb, it begins and finishes on F, with all notes in between being white. Bb is in the F key (B flat).
