If the Player enters a boat or Nether portal while flying, they will still be flying upon exiting. This doesn't seem to be a bug, however the controls will not be those of flying.
MCPE-9335
Fly bug
Resolved
Duplicate
0
(Unassigned)
Unconfirmed
Tablet - Android - Acer Iconia Tab 8
Android 4.4.2
0.12.1 Pre-release
Retrieved
This bug has already been reported! Please go here -> (MCPE-10409) and make sure to do a quick search for your bug before just writing a duplicate ticket. Currently 51% of resolved tickets have been duplicates!