If I may quote from their own website (as they say it much better than I could!):

The Airways Museum is an aviation museum, but with one difference - there are no aircraft! Instead, the Museum houses a collection of national importance that traces the development of Australia's civil aviation airways system through innovation and technical development from it's beginnings in the 1920s to today. The story is told through artefacts and photographs, and illustrates how Australia has often played a leading role internationally in aviation development.