Eleven Italian air officials have gone on trial for manslaughter and negligence over a runway collision which killed 118 people.
The SAS plane ploughed into a baggage hangar
The crash, at Milan's Linate airport in October 2001, was Italy's worst civil aviation disaster.
A Scandinavian SAS passenger jet speeding down the runway in fog collided with a light aircraft, killing everyone on both planes and four baggage handlers.
Relatives of the dead packed the Milan courtroom for the hearing.
The 11 people on trial include an air traffic controller, flight safety officials and management officials from the airport - among them airport director Vincenzo Fusco.
I believe I did my duty when I was with Enav
Former managing director
Five of the defendants were in court for the first hearing, Italian reports said.
They included the former managing director of Enav, Italy's air traffic control agency, Sandro Gualano.
"I believe I did my duty when I was with Enav," the Ansa news agency quoted Mr Gualano as saying outside the
Investigators found multiple problems including no ground radar
He has previously said the crash could have been avoided if fog procedures had been followed.
Five other Enav officials are also on trial, along with two from the civil aviation agency Enac, two from the airport management company SEA and the flight controller.
The SAS plane, an MD-87, was taking off on a flight to Copenhagen with 110 people on board when the Cessna, on a business flight, crossed its path.
The larger plane veered into a baggage handling hangar, killing four people inside.
A report by Milan's public prosecutor said a "death trap" had been set at Linate.
The airport's ground radar system was out of service, even though the airport is frequently hit by fog.
Investigators also found that controllers had used Italian as well as the standard English to address the Cessna crew, and the crew was not asked to read back the tower's instructions.
The inquiry also found that runway signs, markings and lights were confusing, and there was no alarm system to warn that the Cessna had strayed onto the runway.
This trial is like an old wound opening up for us
The victims included Italians, Danes, Swedes, Finns, Norwegians, a Romanian, a Briton, an American and a South African.
"This trial is like an old wound opening up for us," said Paolo Pettinaroli, who lost his son in the accident.
He said punishing those responsible would prevent other tragedies.
The trial is expected to be lengthy, and a second hearing set for 20 June may be delayed because of defence challenges to some prosecution documents.
Linate's procedures have been tightened since the crash, with a reinstated ground radar system, lights and signs along taxiways and the redrawing of confusing maps.