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Hacking incident targeted check-in system on Friday

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London's Heathrow, Berlin and Brussels airports affected

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Brussels set to cancel half of Monday's flight departures

(Adds Collins statement in paragraph 4)

By Sabine Siebold and Christoph Steitz

BRUSSELS/BERLIN, Sept 21 (Reuters) - Some of Europe's

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's 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's Heathrow - Europe's 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's 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.

"For me, it was business as usual. For those poor souls who

didn't do online check-in or have bags to check, they may be

waiting a bit," he said.

Berlin Brandenburg Airport said on Sunday some problems

persisted but that a manual workaround was in place.

"Occasionally, 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," it said.

Heathrow said early on Sunday that work was continuing to

recover from the check-in system outage. It added that "the vast

majority of flights have continued to operate".

An analysis by aviation data provider Cirium said delays at

Heathrow were "low", Berlin had "moderate" delays, while

Brussels had "significant" 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 & Spencer ( MAKSF )

losses in the hundreds of millions of pounds.