Linate Airport was operating without a functioning ground radar system at the time, despite having had a new system approved on 30 March 1995. The previous system had been decommissioned on 29 November 1999, but the replacement had not been fully installed. The new system finally came online a few months later. Guidance signs along the taxiways were obscured, or badly worn, and were later found not to meet regulations. After the pilots mistakenly turned onto the R6 taxiway that led to the runway, there were no signs by which they could recognize where they were. When they stopped at a taxiway stop-marking, and correctly reported its identifier, S4, the ground controller disregarded this identification because it was not on his maps and was unknown to him. Motion sensing runway incursion alarms, although present, had been deactivated to prevent false alarms from vehicles, or animals. The ground controller's verbal directions used terminology to designate aprons, taxiways, and runways, which did not match their on-the-ground signage and labels. Lastly, neither pilot of the Cessna was certified for landings with visibility less than , but had landed at the airport anyway a few minutes before the disaster.