Lava's flow reach is three blocks from the source. However, it will detect and flow towards 'holes' (non-solid blocks lower than itself) father than this distance, up to five blocks from the source.
Tested in creative and survival, with lava blocks placed by the player (via a lava bucket).
Linked issues
Attachments
Comments 10

Affects 0.14.3

Affects 0.15.9. (Tested on Windows 10.)

Affects 0.15.10 & 0.15.90.8 (0.16.0 beta build 5).

Affect 1.0.3 🙂
Affects 1.0.4.0.
Affects 1.0.4.1.
Affects 1.0.5.0.

Affects 1.1.0.1.
This issue appears to be fixed in 1.1.0.9 - Lava will spread out as normal if it can't reach a hole.
Confirmed on Samsung Galaxy Note 3. Android 5.0 Version: 0.12.1 Beta 3