Security officials involved in preparations for the Athens 2004 Olympics yesterday began their first full-scale exercise. Yesterday they had to rescue the passengers of a plane at Athens International Airport, today they must free hostages from one of the luxury cruise ships that will serve as hotels during the Games. In all, some 1,800 specialists, from the police, army, fire brigade, coast guard and special forces, with negotiators, psychologists and academics, are taking part in the excercise. They must «free» the hostages, detain their captors and also deal with a simulated bomb attack on the airport. Media have been barred from watching Rainbow 2002. Security adviser Peter Ryan, head of security at the Sydney Olympics, said authorities were planning for «the unthinkable,» including attacks with biological weapons and nerve gas.