It might seem Optus have not learned much from history. This outage seems to 'rhyme' with the 1990 AT&T network crash.
Main points - a one-line software error caused 70 million uncompleted phone calls and 3 airports in the New York area to shut down
We used to use the AT&T crash as a case study in how not to do software testing, system monitoring, risk management, business continuity planning, project management, etc
I can’t recall (or find now) what it cost AT&T, but it wasn’t cheap (even in 1990 dollars)
A long article about the AT&T outage, with a few pieces extracted
https://web.mit.edu/hacker/part1.html
“On January 15, 1990, AT&T's long-distance telephone switching system crashed.
This was a strange, dire, huge event. Sixty thousand people lost their telephone service completely. During the nine long hours of frantic effort that it took to restore service, some seventy million telephone calls went uncompleted.”
…
“the System Crash of January 15, 1990, was caused by an ‘
improvement’ in software. Or rather, an ‘
attempted’improvement.”
…
(Aviation content)
“AT&T itself had crippled airports with computer malfunctions -- not just one airport, but three at once, some of the busiest in the world.
Air traffic came to a standstill throughout the Greater New York area, causing more than 500 flights to be cancelled, in a spreading wave all over America and even into Europe. Another 500 or so flights were delayed, affecting, all in all, about 85,000 passengers. (One of these passengers was the chairman of the Federal Communications Commission.)”