The question is does the TWU represent pilots?
I cant find a reference to pilots in their awards.
-Their base wages are less (Bus driver 25+ pax or truck driver 100+ tonnes are both less than the GA award for SE).
Fact is that now days some of these guys will sign you up but really havent the facilities or know how to deal with our particular issues & needs. Stick with your relevant union.
(Unless your airline covered by another body this is most likely the AFAP).
It is also interesting to note that the TWU say that they are all about transport safety, however their industry (Truck drivers) has a large reputation of having an element that flaunt the rules (fudged driving times, overloading and pills to keep awake).