A Etihad Airways Airbus A380 comes in through the fog to land at Heathrow Airport in west London on December 30, 2016. - The Met Office issued a yellow warning of fog, advising that "Driving conditions will be difficult with journeys likely to take longer than usual and delays to air travel possible". (Photo by Justin TALLIS / AFP) (Photo credit should read JUSTIN TALLIS/AFP via Getty Images)