It used to be that when you are flying, you can shift while holding space to slow down flight. However now, the speed stays the same. Additionally, consider that sprinting while flying does speed up flying... Due to this bug, controlling flight becomes more difficult.

To test:

1. Go into gamemode 1

2. Fly, and hold spacebar while moving around

3. Crouch and keep moving around holding crouch and spacebar to see that your speed does not change from without crouching.