Considering one of my team literally was carrying a Motorola satellite phone on the NYE/D of 2000-01-01 in case our mobile or land comms went down because the public transit was running all night, we took it very bloody seriously.
If there was an interruption to services on that night in particular, that's a serious public safety issue.
We had tested our system, and integration tested with all the other systems we connected to directly, but any FMECA analysis would show you that there were failure modes that we couldn't mitigate.
So people on planes falling out of the sky? Probably no.
People being crushed in a railway station on NYE? Possible yes.