Thanks for the feedback!
Yeah, a proper tutorial on how to fly would have probably been a good stretch goal if we'd had more time.
What I think is happening here, is that you'll turn more by rolling to the side and then pitching up, rather than trying to pitch with the yaw controls (which tends to be more useful for small, low-speed adjustments). Either that, or you've experienced the plane getting a lot more sluggish in handling once it gets slow (since there is less air flowing over your wings your plane has less force to turn).