I don't know anything about ATC systems. Why should it be possible to continue when a single flight plan is wrong? Naïvely it sounds like having even a single plane in an unknown position would make safe automated control impossible. Is that wrong?
First, you don't understand the purpose of a flight plan. The purpose of the flightplan safety.
You, the captain, are saying "My intention going from A to Z via K,J and X". You then "activate" your flightplan over the radio upon departure.
The purpose of the flightplan is so people on the ground broadly have an idea of where you are and when you'll arrive. The former is to assist with co-ordination between control zones. The latter is so that if the destination airport doesn't see you X hours after your ETA, then they can start searching along the filed route until they find the debris of your crashed aircraft.
Second, you need to take "automation" out of your thinking. Flight crew don't just punch the plan into the nav and sit there twiddling their thumbs.
Shit happens and the crew might need to deviate from the plan. It happens all day every day. There might be some horrible weather ahead that you want to route around. There might be something happening in the airspace around you that ground might want to route you around.
Therefore flight plan merely describes your INTENTION.
To make the system resilient.
Note: When the error happened the flight was not in the air yet. The system in question received the flight plan 4 hours before departure time. If the system would have flagged the flight plan as bad they could have called them and told them that they can't fly. If not that they could have refused them when they were entering the airspace. Can happen any time for any reason.
> Naïvely it sounds like having even a single plane in an unknown position would make safe automated control impossible.
Flight plans are not for knowing the position of the plane.
> Is that wrong?
Slightly.
This is not true. The plan is transferred 4 hours before it is due to enter UK airspace. Big difference. Flights can already be in the air when the plan is transferred.
You are correct.
It sounds to me like the engineers made a design decision between "add handling mechanisms for valid-but-unexpected flight plans" and "ensure we can handle absolutely every valid flight plan"? If so, this is a rare case where I sympathise with the engineering team behind a major IT failure.
Flight crew and dispatchers report that flight plans are regularly rejected, and then they need to file a new one. But it sounds like this rejection happens in a layer before the one which failed in this case.
So this is basically a system which is not meant to be able to reject a flight plan, since the plans it receives were already checked and validated.
The issue should have been caught in one of the higher systems, and then the error should have also been handled in a more appropriate way.
Remember anyone flying IFR needs a flight plan, lots of private pilots etc. Plenty of people make mistakes.