My reading suggests that the problem is not ATC taking sickies, nor is ATC holding the travelling public hostage.
An Australian-domiciled pilot said to me a couple of weeks ago 'there's an element of CFMEU-style tactics in what the Sydney air traffic controllers are doing'.
Sickies appear to peak on Fridays and Saturdays, and during school holidays. Amazing.
No one denies controlling aircraft must be a very stressful, fast paced job. I once worked with a male who was bright, but had applied and been rejected because he couldn't get his head around the multiple types of separation he needed to be able to process.
However many other jobs are arguably equally stressful: paramedics, surgeons, emergency department nurses, train controllers, firemen at times, police, dangling 140 metres above sea level from the Bolte Bridge in Melbourne to remove graffiti painted by Pam The Bird, crane operators on building sites, heavy vehicle and freight train drivers to name a few.
These people signed up for very well remunerated positions in Sydney yet their taking sickies (of which they have an unlimited number available each year) is hugely disadvantaging passengers, some of whom miss international connections as a result, and causing airlines to waste fuel. On occasion, restricted numbers of movements beyond hourly and quarter hour movement limitations may see airline crews having to spend an overnight away from where their roster says they should be.
What justification is for these 'protected species' of ATCs to receive unlimited annual sick leave? I don't know of any other occupation at non-management level that allows this.