It took Optus more than 32 hours to notify the public of a catastrophic failure of its network that dropped at least 600 Triple Zero calls, resulting in the deaths of three people.

The company’s chief executive officer Stephen Rue provided more details about the timing of the company’s crisis at a press conference on Saturday afternoon. Here’s how the crisis unfolded.

Thursday, 12.30am

Optus conducts a routine network upgrade of a firewall, which is a network security system. Initial testing and monitoring do not indicate any problems with calls connecting. There are no “red flags” in terms of call levels “at a national level”, Rue said, but the company does not have any alarms to alert that emergency calls are not connecting.

But virtually immediately after the upgrade begins, a “tech

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