Miniatures of people with computers are seen in front of binary codes and words 鈥渃yber attack鈥 in this illustration taken July 19, 2023. 鈥 REUTERS

BRUSSELS/BERLIN 鈥 Some of Europe鈥檚 biggest airports battled to restore normal operations on Sunday after hackers disrupted automatic check-in systems, with Brussels asking airlines to cancel half of Monday鈥檚 flight departures due to persistent problems.

Hackers on Friday targeted check-in and boarding systems provider Collins Aerospace, owned by RTX, disrupting operations at London鈥檚 Heathrow – Europe鈥檚 busiest airport, Berlin Airport and in Brussels.

Passengers faced long queues, cancellations and delays on Saturday. While the disruption eased significantly in Berlin and Heathrow on Sunday, according to airport officials and data, delays and flight cancellations were continuing.

In a statement early on Monday, Collins said it was working with four impacted airports and airline customers, and was in the final stages of completing the updates needed to restore full functionality.

A spokesperson for Brussels Airport said Collins Aerospace had not yet delivered a secure, updated version of the software necessary to restore full functionality, prompting the airport to seek the flight cancellations on Monday.

Brussels Airport said 50 of Sunday鈥檚 257 scheduled departures had been cancelled to avoid long queues and last-minute cancellations. A day earlier, 25 of the planned 234 outgoing flights were cancelled, the airport operator said.

RTX said on Saturday it was working to fix the issue as quickly as possible, and that the disruption could be mitigated with manual check-in operations.

It said the incident had impacted its MUSE software, which is used by several airlines.

One passenger flying from Brussels said the disruption to his journey had been minimal.

鈥淔or me, it was business as usual. For those poor souls who didn鈥檛 do online check-in or have bags to check, they may be waiting a bit,鈥 he said.

Berlin Brandenburg Airport said on Sunday some problems persisted but that a manual workaround was in place.

鈥淥ccasionally, there are longer waiting times at check-in, boarding, baggage handling and baggage reclaim. Delays to departing flights today are in line with a normal operating day,鈥 it said.

Heathrow said early on Sunday that work was continuing to recover from the check-in system outage. It added that 鈥渢he vast majority of flights have continued to operate鈥.

An analysis by aviation data provider Cirium said delays at Heathrow were 鈥渓ow鈥, Berlin had 鈥渕oderate鈥 delays, while Brussels had 鈥渟ignificant鈥 delays.

Regional regulators said they were investigating the source of the hacking, the latest in a string of hacks to hit sectors from healthcare to autos. A breach at carmaker Jaguar Land Rover halted production, while another caused Marks & SpencerMKS.L losses in the hundreds of millions of pounds. 鈥 Reuters