Disruption caused by thick fog is expected to continue at Gatwick Airport until the end of the day on Sunday, the airport’s busiest day of the holiday period. Nats, the UK’s main air traffic control provider, said temporary air restrictions were in place for the remainder of the day because of low visibility in airfields affected by fog.

More than 1,000 flights were delayed at London Heathrow and Gatwick on Friday as fog created travel chaos for UK airports.

Travelers flying to or from the U.K. are facing further disruptions as thick fog and low visibility restrict air traffic on one of the year’s busiest weekends.