KEY WEST - The Cuban government will allow the pilot and steward of a Cuban airplane to testify against a man accused of hijacking the plane to the United States with bogus grenades three months ago.

Opening statements are to begin today in the trial of Adermis Wilson González, 34, the man accused of commandeering the Cubana twin-engine plane to Key West on April 1 after unusual negotiations by Cuban President Fidel Castro and top U.S. diplomat James Cason failed.

The Antonov AN-24's pilot, Jorge Armando Rojas, and steward, Salvador Requeny Robles, arrived in South Florida with a Cuban government escort over the weekend.

Rojas and Robles elected to return to Cuba after the hijacking, as did most of the passengers and crew.

Havana's cooperation in the case is noteworthy but not unprecedented: The Cuban government has cooperated with federal prosecutors in migrant-smuggling cases and allowed the Cuban captain and first mate of a fishing boat to testify in the 2000 trial of three men from India and Pakistan accused of hijacking the boat from Marina Hemingway to Key West.

Also expected to testify for the government are several Cuban passengers who decided to remain in the United States after their unexpected diversion. Under U.S. immigration policy, Cubans who reach U.S. soil are usually allowed to stay.

U.S. District Judge Shelby Highsmith seated the four-woman, eight-man jury Monday for a trial that is expected to last one week. Wilson faces 20 years in prison if convicted.

Officials with the U.S. State Department declined to comment on the trial or the cooperation of their Cuban counterparts. A spokesperson for the Cuban Interests Section in Washington did not return phone calls.

The Antonov AN-24 departed March 31 from Nueva Gerona on the Isle of Youth off Cuba's southern coast for what was to be a 30-minute flight to Havana. Toward the end of that flight, U.S. investigators say, Wilson jumped up, began waving ceramic grenades and demanded to be taken to Florida. But the plane didn't have enough fuel and landed instead at José Martí International Airport in Havana.

Wilson's common-law wife and 3-year-old boy were also on the plane. Prosecutors contend that Wilson assembled the fake explosives using metal objects that his wife had hidden in her hair. She has not been charged.

The plane sat on the airfield in Havana for about 12 hours as Castro and Cason tried to negotiate Wilson's surrender. He demanded milk for his child and $250 and released some of the passengers, but he made the pilot take off after the plane had been refueled.

On landing in Key West, the plane was met by federal agents, and Wilson gave up without a fight. His wife and child remain in the United States.

The flight from Cuba occurred as U.S.-Cuba relations were sharply deteriorating and as Cuba's government was cracking down on dissidents. Two other Cuban planes had been hijacked in the preceding six months.

One day after Wilson's alleged hijacking, another group of Cubans took control of a Havana passenger ferry and tried to steer it to Florida, but the boat ran out of fuel at sea.

Less than two weeks later, three of those hijackers -- who reportedly had been armed with a pistol and knives -- were executed in Cuba by firing squad.

U.S. officials are hoping that this week's trial will deter would-be Cuban hijackers.

On the eve of trial Monday, however, the defendant pulled an 11th-hour surprise. Wilson asked Highsmith to allow Tampa attorney Ralph Fernández to represent him along with his appointed counsel, Stewart G. Abrams.

Fernández has represented alleged Cuban hijackers before, and his clients also include Brothers to the Rescue founder José Basulto.

''I truly, 100 percent place my trust in that gentleman,'' Wilson told the judge. ``This is a matter I wished to have brought to you before, your honor, but I just didn't have the opportunity.''

Fernández said in a telephone interview that he would be interested in taking the case -- if the judge would postpone the trial so he could subpoena Castro and Cason.

''I think the jurors should hear from Mr. Castro,'' Fernández said.

On Monday afternoon, that appeared unlikely.

''If [Fernández] appears tomorrow morning at 9:30, I will question him and then see what happens,'' Highsmith said Monday. ``However, I will not delay the trial.''