Just installed
Through Steam
No mods
Played only tutorials
One game session - not restarted
There's an overlay in tutorials, showing me how to pitch (animation showing arrow up and down, S and W)
Restarting the game fixes the issue. Going out of tutorial and back does not fix it.
Could have been caused by me having to restart the first controls tutorial, since it did not register that I pitched up again, even though I flew entirely straight up.