A cyberattack on a provider of check-in and boarding systems has disrupted operations at several major European airports including London's Heathrow, the continent's busiest, causing flight delays and cancellations on Saturday.

Collins Aerospace, which provides systems for several airlines at airports globally, is experiencing a technical issue that may cause delays for departing passengers, Heathrow Airport said, having warned of delays.

Brussels Airport and Berlin Airport were also affected, they said separately. RTX, Collins Aerospace's parent company, said it was aware of a "cyber-related disruption" to its software at selected airports, without naming them.

Hours later, Dublin Airport said it was also facing minor impact from the issue, along with Cork Airport, Ireland's second biggest after Dublin.

"The impact is limited to electronic customer check-in and baggage drop and can be mitigated with manual check-in operations," RTX said in an emailed statement, adding that it was working to fix the issue as quickly as possible. It did not give any information on who might be behind the attack.

At Heathrow, Berlin and Brussels, 29 departures and arrivals have been cancelled so far, aviation data provider Cirium said. In total, 651 departures were scheduled from Heathrow, 228 from Brussels and 226 from Berlin on Saturday.

Passengers left in the dark

Passengers with a flight scheduled for Saturday were advised by the affected airports to confirm their travel with airlines before heading to the airport.

Tereza Pultarova, a journalist, spoke to BBC News from inside Heathrow, where she was due to fly to Amsterdam for a connecting flight to Cape Town.

"Unfortunately, the airline I'm with ... they don't have a service desk here, so we've been left in the dark," she said. "It's been great chaos, and it's been quite ... frustrating for most people here," she said.

At Berlin Airport, Kim Reisen was struggling with delays and a lack of clarity, telling Reuters passengers had only been told there was "a technical fault."

Another traveler, Siegfried Schwarz, also from Berlin, said: "I ... find it inexplicable that, with today's technology, there's no way to defend yourself against something like that."