Pan-European air navigation authority Eurocontrol expects normal network management operations to resume late on 3 April, after a failure of the crucial Enhanced Tactical Flow Management System.

The ETFMS balances traffic demand over the European network against available capacity of air traffic control sectors.

It achieves this by using flightplan information, filed through a flightplan processing system by aircraft operators, to calculate demand.

The ETFMS has a slot-allocation function to ensure that the capacity is available to meet the demand.

But a failure in this system meant that flightplans filed before 10:26UTC on 3 April were lost, forcing aircraft operators to refile all flightplans for aircraft that had not already departed.

Eurocontrol subsequently moved to an air traffic flow management contingency plan, but this has effective cut European network capacity by 10% – a substantial reduction in such busy airspace.

Some 50% of the 29,500 flights expected across the European network today "could have some delay" as a result of the problem, says Eurocontrol.

The authority stated at 16:49 that slot allocation by the ETFMS had been restored, and that a "move to the recovery phase has begun".

It adds that flights will be subject to calculated take-off times from 18:00UTC.

Eurocontrol says the centralised code assignment and management system – which is designed to address transporter squawk code scarcity by making efficient use of available codes – is operating in contingency mode and expects this to continue until midnight. The system will be restarted at 22:00.

The air traffic flow management contingency plan will remain in effect for several more hours, until the authority can be certain that the system is able to operate normally.

While the regulation of traffic is affected by the problems, Eurocontrol stresses that air traffic control is not. "There are no safety implications arising from this incident," it says.

Source: Cirium Dashboard