What goes around
While awaiting the September update from Cairns Airport the BITRE have updated national numbers for July. Top 20 airports summary growth for the year to July:

This time I have included Proserpine which has distorted numbers following the impact of Cyclone Debbie on the Whitsundays when it replaced Hamilton Island in the top 20. Monthly comparison with July last year:

Rockhampton is a bit of a mystery there and comes off the back of a big number the previous July so should probably be taken as an outlier. Launceston plays catch up with Hobart. Mackay and Karratha now up near the top.
BITRE post monthly numbers for the top 20. They only post annual numbers beyond that. So an annual comparison of passenger numbers for Proserpine and Hamilton Island:

The increased share at Proserpine was evident before Cyclone Debbie but now looks to be reverting somewhat again. This could come into play when we consider the Productivity Commission inquiry into economic regulation of airports. Not sure I can think of two such closely located airports servicing a defined market?
I only browsed a couple but Gold Coast inquiry submission was emphatic that airport competition was more significant in SEQ. The BITRE top 20 airports by state comprises Queensland (8); NSW (3); WA (2); Tas (2); NT (2); Vic (1); SA (1); ACT (1). Karratha is currently #20 and Broome also lurks at #21 ready to pounce.
Meanwhile the numbers at Cairns continue to look a bit lame.