MIAMI, NOV. 4 -- Federal agents have smashed a large, sophisticated drug transport ring that used spotter planes, infrared beacons and decoy plane passengers called "cover girls" to avoid detection, authorities said today.

An indictment unsealed today named 30 defendants, including several American pilots. The Miami-based ring was contracted by the Medellin cartel, the Colombia-based drug-smuggling organization responsible for 80 percent of U.S. cocaine imports, to haul cocaine from Colombia to the United States, investigators said.

"This was the largest transportation network used by the Medellin cartel between 1982 and 1986," said Bill Perry, acting special agent in charge of the Miami Federal Bureau of Investigation office. During that period, the ring hauled 20,000 pounds of cocaine in 19 shipments, the indictment said.

Investigators said the ring may have smuggled in as many as to 60,000 pounds of cocaine over those four years and were paid about $90 million by the cartel, a U.S. Customs spokesman said.

Loads of cocaine flown out of Colombia were dropped in Bahamian waters for later pickup by boats, which then would smuggle the drugs to the Florida coast, according to the indictment.

Patrick O'Brien, head of the U.S. Customs Service here, said the ring had radio-infrared beacons -- giving rise to the case's code name, "Operation Beacon" -- attached to cocaine loads dumped at sea. The loads would float just below the surface but could be located by spotters with radio receivers or infrared goggles, O'Brien said.

The smugglers stationed an observer at a Miami condominium to keep track of Customs and Coast Guard vessels, O'Brien said, and had a radio room in Miami to communicate with their planes and boats and Colombian and Bahamian contacts.

O'Brien said a man whom the ring contacted to build the beacons also had worked with Customs and gave authorities information.