By FRED STRASSER
And LIZ BALMASEDA
Herold Staff Writers

A thin man in a black beret who claimed to be "Lt. Spartacus" of the Black Liberation Army hijacked a Miami-bound airliner carrying 57 passengers and crew to Havana Tuesday afternoon.

Immediately after Piedmont Airlines Flight 451 landed at Havana's Jose Marti International Airport at 4:24 p.m., Cuban security officers took the unidentified man into custody, U.S. officials said. The Boeing 737 finally landed at Miami International Airport at 6:59 p.m.

It was the first hijacking of a domestic flight to Cuba this year and the 12th such incident since May 1.

The flight, which originated in Newark, N.J., with stops in Charlotte, N.C., and Charleston, S.C., was commandeered at 3:43 p.m. as it made its final descent into Miami.

 Bill Perry, FBI assistant special agent in charge of the Miami office, drew an account of the hijacking after agents interviewed passengers and crew members.

As the plane made its final approach into Miami International Airport at 3:17 p.m., the hijacker pushed his call button to request a flight attendant. When she arrived, the man handed her a note saying that there were explosives aboard the plane that could be detonated by two, accomplices who were also aboard.

The hijacker also demanded $5 million, but did not say from whom or where it should be delivered.

The pilot, Capt. Carl Gamble, then spoke with the hijacker over the plane's intercom and told him he would take him to Cuba. The hijacker warned Gamble not to alarm passengers or mention their destination. He then locked himself in the bathroom and scrawled a message on the lavatory door.

"This was necessary. I would not have hurt anybody at this point. But the time will come when we will meet as enemies. I'm sorry for this. I have responsibilities and duties. I am a soldier," said his message.

After a futile search for hidden explosives in the plane at Miami International Airport, FBI agents removed the bathroom door and carried it through the terminal, drawing curious stares from bystanders.

The hijacker, in fact, had no accomplices.

When Cuban authorities cleared the plane, they arrested only one man. Investigators were still comparing the names on the passenger manifest in an effort to determine where the man boarded the plane and what name he used.

One passenger, Brian Ahern of Summerland Key, Fla., watched the mysterious passenger, described as being in his late 20s and about 5-foot-9, enter the lavatory. Ahern said he overheard a conversation between the man and a flight attendant through the bathroom door. In what he described as broken English, Ahern said he heard the man demand "safe passage to Cuba" and say that he was with "BLA."

Bill Abercrombie of Miami, toting two bottles of Cuban rum bought while in the Havana airport, said he watched what he described as a "Cuban SWAT team" board the aircraft and come out with one prisoner who was put into a car.

Judy Strippelhoff of Lexington, Ky., said that although there was no official announcement of a hijacking, passengers had a "pretty good idea" where they were going.

"The no-smoking and seat belt lights were on. Suddenly they were off. The stewardess said 'we are going to make an unscheduled landing.' She didn't say where. But, you know, this is Miami," she said.

While the passengers and crew members of Flight 451 waited for clearance in Havana, a small cluster of friends and relatives awaited nervously it Miami International Airport.

"Sure, I'm worried. Anything can happen in these things," said Babe Lavivona, who waited for his 32-year-old daughter, Karen, who, boarded at Charlotte.

One woman, waiting for her husband, was less concerned.

"Why should I worry?" asked the woman who would not give her name. "This has happened before. I hear they go shopping."

Piedmont spokesman Donald McGuire, who flew to Miami from airline headquarters at WinstonSalem, N.C., during the incident, said he didn't know what the hijacking would cost the airline.

"The Cubans didn't mention anything about fees. They just sold us 10,000 gallons of fuel and we left," he said.

Tuesday's hijacking, McGuire said, was the first time a Piedmont flight was successfully commandeered.

Officials at the Miami Airport stopped two men before boarding a Piedmont flight to Tampa on Sept. 14 and charged them in a suspected hijacking attempt. Two other attempted hijackings were thwarted in the air by passengers who overpowered air pirates.

It was the first hijacking to Cub since Sept. 22, when a New York to Virgin Islands flight was diverted after a man with a black box claimed to have a bomb and demanded to go to Havana.

Shortly after the rash of hijackings started last year, the FAA announced it was stepping up security measures by placing sky marshals aboard certain flights and making more thorough baggage checks. FAA spokesman Jack Barker said there was no sky marshal aboard Flight 451.

Tuesday's hijacking was the second involving a U.S. airliner this year. The first occurred on Feb. 11 when a Haitian soldier armed with machine gun and hand grenades hijacked an American Airlines Boeing 727 en route from Haiti to New York, which was already the flight's destination.