Flight is not maintained when passing through portals

If I fly into a neither portal, on the other side I am walking.

What I expected to happen was...:
Flying into a nether leads to flying out the other side

What actually happened was...:
Flying into one side results in walking on the other side

Steps to Reproduce:
1. Put your character in flight mode
2. Fly into nether portal
3. Notice, in the other dimension, the player is walking.

edit:

Duplicate of MC-1701, but more detailed.