Debbie destroys data
BITRE have now updated airport numbers to March which provides a better indication of the combined impacts of an earlier Easter and last year’s Cyclone Debbie.

Debbie made landfall in the Whitsundays on March 28 2017. As a consequence Hamilton Island has now been removed from the top 20 summary to be replaced by Proserpine. This is unlikely to be sustained. It also results in some big monthly growth numbers for Mackay and Townsville compared to last year.
The earlier Easter looks to have bumped up the national March growth numbers around 2-3%. A comparison of annual top 20 growth performance (ex Proserpine):

Meanwhile Cairns has reverted below the mean:

The largest airports at Sydney and Melbourne above the national average is mostly a consequence of their position as the largest international gateways:

Worth a look at the recent March quarter commentary from Qantas.
Group Domestic Unit Revenue increased by 8.0 per cent compared to the prior corresponding period. This reflects strong demand across key markets, including continued recovery of the resources sector and gains within the small-to-medium enterprise segment. The timing of Easter, which fell partly in the third quarter in FY18 compared with the fourth quarter of FY17, also increased demand for leisure travel compared with the prior corresponding period. Group Domestic capacity decreased by 1.9 per cent.
Guess Alan Joyce could enjoy another adequate bonus this year.
Source: BITRE (BITRE data is revenue passengers on scheduled flights so will vary slightly from that posted by Cairns Airport)