The core issue is, when the British came to Australia there were people already living here. It is evident they were here for a very very long time, so long in fact they are considered the first inhabitants of this land or by definition, Aboriginal. There is a flag that represents this fact and is freely available for public use. Considering what it represents it should given sufficient exposure to become readily identified as being associated with Australia. There are Australian aircraft that fly around the nation and overseas, many of these aircraft have a flag painted on their external surface, why not add the Aboriginal flag?