FORT LAUDERDALE, Fla. -

An American who returned from Cuba decades after hijacking a jetliner to the communist island has pleaded guilty to a kidnapping charge in South Florida federal court.

The plea was entered Thursday by William Potts, who said he returned last year from Cuba to resolve the 30-year-old U.S. case.

The kidnapping count replaces a charge of air piracy, which carried a mandatory prison sentence of at least 20 years.

His attorney said Potts, 57, is seeking credit for 15 years he served in a Cuban prison. He still faces a maximum life term when he is sentenced in July.

The FBI said Potts claimed he had explosives when he hijacked a New York-to-Miami flight to Havana in 1984. He described himself then as a black militant calling himself "Lt. Spartacus."