When you start flying you fly like normal. However, after a certain time you start walking in mid-air and now don't move as quickly or fast fly, just sprinting like you are running. It behaves exactly like you are on the ground, it even makes a noise when you go over blocks which are a couple of layers below.

Also, I'm actually on v1.4.2 but there is no option for it above. It doesn't have an update as well.