Officials say a two—day strike by British public sector workers could cause disruption at the country’s ports and airports.

Up to 270,000 civil servants are taking part in the 48—hour action, which is expected to affect transport hubs, courts, and police emergency call centers.

The Public and Commercial Services Union says it’s striking over changes to their layoff and entitlement packages.

Heathrow Airport, Europe’s busiest, said the strike was expected to affect service at border control for passengers arriving into Britain starting Monday morning.

The airport said passengers should expect some additional delay going through immigration.

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