Nearly half of all European flights may suffer delays today after a system failure at Eurocontrol, the air traffic coordinating body for the European Union, interfered with the ability to manage air traffic demand and capacity, according to the BBC. The system, known as the Enhanced Tactical Flow Management System, is responsible for managing the flow of European air traffic — as well as flights to North Africa and parts of the Middle East — on a daily basis. Eurocontrol operates out of Brussels, Belgium and is responsible for managing around 30,000 flights per day from 41 member states.

The error has forced Eurocontrol’s contingency plan, which involves reducing network capacity by grounding planes starting with 10 percent. However, as the delays build and more planes are grounded and waiting for takeoff, the number of affected flights is expected to grow rapidly and could affect as many as 50 percent of all daily air traffic.

The actual air traffic systems of individual airports are not in jeopardy, Eurocontrol stressed, meaning air travel remains safe and unaffected. However, airport management is severely restricted in its ability to clear planes for takeoff due the system failure, with the BBC reporting some airports clearing only 10 takeoffs per hour. Eurocontrol also says the system failure resulted in the loss of thousands of flight plans, which airlines now need to resend.

There has been a failure of the Enhanced Tactical Flow Management System. Contingency procedures are being put in place which will have the effect of reducing the capacity of the European network by approximately 10%. Further information will be provided as soon as possible. — EUROCONTROL (@eurocontrol) April 3, 2018

The issue with the ETFMS has been identified and work is progressing to recover the system, which is expected to occur late this evening. Aircraft operators are requested to refile any flight plans for flights not yet operated and that were originally filed before 10.26UTC — EUROCONTROL (@eurocontrol) April 3, 2018

We very much regret the inconvenience caused to passengers across Europe today however safety is our number 1 priority at all times. We are working hard to ensure the network returns to normal operations over the coming hours. — EUROCONTROL (@eurocontrol) April 3, 2018