Not a big fan of gulls myself. I wouldn't be surprised if they kept their heads level because they don't have the brain power to recompute trajectory if the ground is crooked.
I take a lot of photos of seagulls flying. I delete 99% of them immediately.
One thing I notice in all the photos, whatever the position of the wings and body, the head is always in a normal ? position. Eyes horizontal, beak usually straight ahead.