Steps to reproduce

1. Toggle flight on in creative mode (double tap space bar).
2. Descend until your feet touch a solid surface (hold shift key).
3. Try to move around.

Expected result

Touching a surface with your feet while in flight mode has no effect on your speed.

Observed result

You get locked into sneaking speed. This is despite still being in flight mode and not sneaking (paper doll does not crouch). The only way to turn off this sneak speed is to exit flight mode (double tap space bar).