Airmails
Australia's first airmail-designated stamp appeared on 20 May 1929. A special 3d (three pence) airmail stamp was available for mail sent on the Perth-Adelaide air service. The cost of this service was 3d per ½ oz plus normal postage. On 19 March 1931 and 4 November 1931, a further two airmail-designated stamps, both 6d (sixpence), appeared. After these, general definitives were used for mail sent by air.
Read more about this topic: Postage Stamps And Postal History Of Australia