I used commands to apply high levels of speed, so I could fly very quickly, but this did not work.

How to reproduce:

1. Use the command /effect @s speed 100 255.
2. Start walking, and notice yourself moving extremely fast.
3. Enter flight mode, and notice that you fly at normal speed.

I expected my flying speed to be much faster with the status effect, as described in Step 2, but it did not. Slowness also has no effect on flying in creative.

This may be intentional, but I figured I would report it.