Flight disruption across Europe is set to continue, with Brussels airport in Belgium asking airlines to cancel nearly half of their flights on Monday.

Several of Europe's busiest airports have spent the past few days trying to restore normal operations after a cyber-attack on Friday disrupted their automatic check-in and boarding software.

Disruption had eased significantly in Berlin and London Heathrow by Sunday, but delays and flight cancellations remained.

In a statement on Monday morning, software provider Collins Aerospace said it was in the final stages of completing necessary software updates.

Brussels Airport stated the service provider is actively working on the issue but it was still unclear when the issue would be resolved.

They have requested airlines to cancel nearly 140 of their 276 scheduled outbound flights for Monday, according to the AP news agency.

Heathrow also reported ongoing efforts to resolve the issue and apologized to customers facing delayed travel, emphasizing that the vast majority of flights have continued to operate while urging passengers to check their flight status.

About half of the airlines at Heathrow were reportedly back online by Sunday, using backup systems to manage operations.

A spokesperson from Berlin Airport indicated manual boarding was still in use for some airlines, with no clear timeline for the resolution of the electronic outage.

The UK's National Cyber Security Centre is collaborating with Collins Aerospace and impacted airports to understand the incident's impact. Cybersecurity threats in the aviation sector reportedly increased by 600% last year, raising significant concerns about system vulnerabilities.