After you go inside a mob which is standing on the ground (example: a Spider) then change to creative mode then you are standing on one pixel of air.

Well, recently i have been playing around with spectator mode and i got to the inside a spider, then i switched to creative mode, then something strange happened. I was flying on one pixel of air. Way to reproduce: 1. Go to spectator mode (/gamemode 3), 2. Go inside a mob which is standing on the ground (left click) 3. Go to creative mode (gamemode 1). There is no way how i could fly on one pixel of air. mMybe it's a misunderstanding. Normally, when you try to fly on 1 pixel of air, it's impossible.