I don't think it matters that much, I know of 2 people dressed just as you propose that got a job in Darwin in the last 6 months. Otherwise agree with 172heavy - hopefully its the attitude they are interviewing apart from in my personal opinion the pilot shirt doesn't matter. If I was doing any interviewing up here I would say as long as you were tidy and presentable that would be ok, personal opinion I would avoid a tie..... but thats just my opinion from having lived up here for some years.