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. The worst affected airline was of course British Airways, as the largest operator at the airport. Emergency autoland Garmin Aviation started studying an emergency autoland feature in 2001 and launched the program in 2010 with more than 100 employees, investing around $20 million. Flight tests began in 2014 with 329 test landings completed in a Cessna 400 Corvalis and another 300 landings in other aircraft. The feature is activated by a guarded red button on Garmin G3000 avionics, evaluating winds, weather and fuel reserves to select a suitable diversion airport and taking over the aircraft controls to land, it advises the ATC and displays instructions to occupants. A Piper M600 single-engine turboprop aircraft began flight tests in early 2018 and completed more than 170 landings to seek pending FAA certification, which it achieved in 2020. Providing access to more than 9,000 runways over , it is offered from 2020 for $170,000 including extra equipment. It was also certified for the single-engine Cirrus Vision SF50 jet that same year, landing on runways over , the SOCATA-Daher TBM 900, and will eventually be certified on other aircraft. In June 2021, the Garmin Autoland system won the 2020 Collier Trophy, for "the greatest achievement in aeronautics or astronautics in America" during the preceding year. Systems A typical autoland system consists of an ILS (integrated glideslope receiver, localizer receiver, and perhaps GPS receiver as well) radio to receive the localizer and glideslope signals. The output of this radio will be a deviation from center which is provided to the flight control computer; this computer which controls the aircraft control surfaces to maintain the aircraft centered on the localizer and glideslope. The flight control computer also controls the aircraft throttles to maintain the appropriate approach speed. At the appropriate height above the ground (as indicated by the radio altimeter) the flight control computer will retard the throttles and initiate a pitch-up maneuver. The purpose of this "flare" is to reduce the energy of the aircraft, reducing