Optus waited almost a day before it told the public that its triple-0 outage caused three deaths, also keeping the government in the dark while executives held several meetings and prepared talking points.

The telco’s senior leadership appeared before a Senate inquiry on Monday, where chief executive Stephen Rue said he was “deeply sorry” about the outage but defended his own actions and resisted calls to resign.

It also presented a detailed timeline, revealing company staff first learned on Thursday night that hundreds of calls had been affected and that there had been deaths. Senior executives including Mr Rue knew early on Friday morning.

Despite this, the regulator, the Australian Communication and Media Authority (ACMA) and Communications Minister Anika Wells were not told until that afternoon, just before Mr Rue fronted cameras. Instead, they were left believing only 10 calls had been affected, as they had been told the day before.

Mr Rue said Optus had taken several steps to improve its processes, including daily triple-0 test calls, protocols to check triple-0 connectivity during upgrades, and plans to move its call centres for emergency situations from Manila back onshore.

But the chief executive blamed staff below him for failing to alert him earlier. The timeline shows frontline staff making welfare calls had learned of two deaths by 9pm on Thursday.

This was relayed to a junior executive just after 11pm, who emailed it on to superiors shortly after midnight. But that message was not read until the next morning, and Mr Rue himself was not called until 7:37am, a call he missed and returned at 8:13am.

Asked whether he and other executives should have been proactively checking for updates on the Thursday night, Mr Rue said he had “an expectation … that anything that came out [of the welfare checks] would be escalated”.

11 crisis meetings held on Friday

Once he learned of the scale of the outage, Mr Rue first informed parent company Singtel and sought to contact Optus chair John Arthur, who was on leave. He also told the board.

In total, 10 meetings were held throughout Friday, variously involving executives and the board. ACMA chair Nerida O’Loughlin was told at 2:36pm, but the communications department and Ms Wells’s office had to find out through ACMA.

They subsequently contacted Optus in a flurry of calls starting just before 4pm. Until this time, both ACMA and the minister’s office were under the impression that only 10 calls had been affected, given on Thursday.

The press conference would not start until 5:45pm, with a delay while talking points were shared with the board and with Singtel.

SA Premier Peter Malinauskas had to call Mr Rue personally that night for information, while WA Premier Roger Cook was contacted the following day. Two of the three deaths were in SA and one in WA.

Difficulty finding out who was affected

Optus executives were also questioned about why it took so long to detect the outage in the first place, which was triggered during a routine infrastructure upgrade just after midnight on Thursday, September 18.

The upgrade itself was carried out by Nokia on behalf of Optus. Staff from both companies were aware of call failures quickly, but did not know they were triple-0 calls and did not identify the source of the failures.

Hours later, the Optus call centre began to receive calls about difficulty connecting to triple-0, but did not escalate it. Optus operating staff became aware when the SA Ambulance service alerted them at 1:15pm. The incident was fixed at 2:34pm.

Optus email mishap left department in dark

The telco operator sent two emails about its outage, which understated its extent, to a departmental email address that had been changed a week earlier.

At that time, it was thought the outage affected only 10 calls, but a message exchange between senior staff showed some confusion about this.

“Is it only fixed line calls that go through the [affected infrastructure]? Is that why the numbers were low?” a staff member asked at 2:55pm.

Throughout the afternoon, Optus encountered difficulty figuring out who had been affected, so that it could conduct welfare checks.

Call logs provided by Nokia were not helpful, because the failed calls had not made it through to be logged in the first place. Optus engineers had to comb internal systems to figure out who had been affected and soon identified 100 affected calls.

Those 100 people were contacted on Thursday, but by the end of the night another 524 had been identified, who were contacted the following day.

Optus has appointed Kerry Schott to conduct a review of its internal processes, and Mr Rue has pledged to abide by the findings of that review.

The Senate inquiry, set up by the Greens and the Coalition, will probe other telcos and examine the actions of government agencies and the minister with a view to identifying any changes that need to be made to triple-0 arrangements.