"G'day" VS AIP
"ABC contact Melbourne radar 135.7, g'day"
"135.7 ABC g'day"
So it's considered by many in Australian aviation to be etiquette, and by others as unprofessional.
I know many pilots who say it out of politeness, some who say it as gratitude for the help ATC has given and some who say it purely out of habit.
My question to the controllers out there is what do you think of saying a good ol' g'day?