Pilots of an Italian Airbus A319 lost horizontal visibility during a non-precision approach to Palermo, before the aircraft crashed short of the runway, investigators have disclosed.
The Wind Jet aircraft, operating a service from Rome Fiumicino, had initially been cleared to descend to 5,000ft (1,520m).
But before reaching the starting point of the authorised instrument procedure, the crew contacted Palermo approach control to request deviation from the planned route, to avoid cloud formations northwest of the airport.
Palermo weather data issued over the course of the evening indicated storm activity in the vicinity and also included warnings over possible windshear.
The radar controller approved the request and vectored the A319 to a point some 6nm (11km) from the Raisi VOR-DME located at the airport, for the non-precision procedure - known as VOR-Z 07 - to Runway 07.
Until this point the aircraft had experienced only light turbulence. But Italian investigation agency ANSV said: "During the approach, while stabilised on the radial and descent profile, the aircraft encountered a strong squall which reduced horizontal visibility."
While the first officer had been the flying pilot, the captain took over the aircraft for the final part of the approach.
But information from the flight data recorder shows the A319 failed to reach the touchdown zone, striking the ground just before the beginning of the runway-end safety area. ANSV says the aircraft bounced onto the runway and skidded for 850m before coming to rest partly on the grass to the left of Runway 07.
The aircraft's main landing gear collapsed during the impact and the jet tore through the localiser antenna for the opposite-direction Runway 25, wrecking it.
There were no fatalities among the 124 passengers and five crew members, despite some injuries, but the A319 (EI-EDM) was written off in the 24 September 2010 crash.