Both terminals at Gatwick Airport are suffering a severe water outage, with passengers being given bottled water.
The toilets cannot be flushed and hand-washing facilities are not working.
Passengers posted online saying they were also unable to get coffee or fill up their bottles from water fountains.
Restaurants were also closed.
Staff at the North and South terminals were handing out bottled water to passengers.
Flights are unaffected.
In a statement on social media the airport said: "A water issue in the Horley area is causing disruption at the airport this morning.
"The problem is affecting water supply in both terminals and is currently under investigation.
"Bottled water is being made available to passengers and staff across the airport and other contingency measures are being put in place to ensure the welfare of our passengers. We will provide further updates and apologise for any inconvenience to passengers."
SES Water, which serves the airport, said: "We have an issue at our Bough Beech Water Treatment Works with some customers experiencing either low water pressure or loss of supply. We apologise to everyone affected by this incident.
"We are working hard to return water supplies to normal."
Residents in Horley and the wider Gatwick area also reported losing their water supply, according to local media.
(c) Sky News 2026: Gatwick Airport suffers major water outage with people unable to flush toilets
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