Just listening the usual journalistic blather about "why no backup system?". Of course there is an online backup system to automatically switch to, but this almost exclusively caters for only hardware errors. In the case of the "erroneous FPL" scenario I described earlier <
U.K. NATS Systems Failure> it was a problem in the software logic, and the backup system runs the same software.
What happened (AIUI) was the NAS programme "FLOPed" (Functional Lapse of the Operational Programme) – aka crashed. The programme was restarted successfully, but when the recovery data (the data that is in the system – including FPLs – that is recorded as a backup from time to time) was read in it FLOPed again. The rogue FPL was in the recovery data.
Eventually the system was restarted using a recovery data set recorded before the erroneous FPL was entered. Phew, everything hunky-dory again.
Until the originator of the rogue FPL realised it was no longer in the system so re-entered it....
