The Global Explorer fare allows travel on QF codeshares operated by Air Vietnam. Not sure if the Circle Pacific rules are equally generous (historically they have lagged behind the GE product). The oneworld web site rules prohibit it (but maybe these are the current rules). On the face of it you have to do a GE and not DCIRC22 fare (obviously considerably more expensive). See
http://www.oneworldalliance.com/prod...fm?ObjectID=28