The wheel turned full circle in December 2006 when London Heathrow was affected for a long period by dense fog. This airport was operating at maximum capacity in good conditions, and the imposition of low visibility procedures required to protect the localizer signal for autoland systems meant a major reduction in capacity from approximately 60 to 30 landings per hour. Since most airlines operating into Heathrow already had autoland-equipped aircraft, and thus expected to operate as normal, massive delays occurred.