Along the same line as Tapatalk, vBulletin has a "Mobile Suite" ap called Flyertalk in the smartphone ap stores that has most of the functionality of Tapatalk. Just go to the ap stores and search for Flyertalk.

If I'm not mistaken, IB owns both vBulletin, and Flyertalk.com.

As a vB forum admin elsewhere, I've tried Tapatalk, and was not happy with the server side integration aspect, plus the constant updates I was having to upload. Conversely, I haven't installed the vB mobile suite on my site because
of the annual cost and lack of interest from the users.