By ABBY GOODNOUGH
 
EY WEST, Fla., Dec. 11 — Six Cuban men were convicted today of hijacking a commercial airliner from Cuba to Key West in a case that heightened tensions between the White House and Cubans in both Havana and South Florida.

Prosecutors had argued that the six hijackers used knives and an ax to take control of a flight from the Isle of Youth, off the southern coast of Cuba, to Havana on March 19. American fighter jets intercepted the plane and escorted it to Key West International Airport. None of the 31 passengers or 6 crew members were injured.

The men, ages 21 to 31, face mandatory 20-year prison sentence and possible life terms for their conviction on air piracy charges.

Each defendant had also been charged with conspiracy to commit air piracy, conspiracy to interfere with the flight crew and interfering with a flight crew.

Three of the men were found guilty of the three additional counts, while the other men were acquitted on some counts.

The jury arrived at its decision after deliberating for six hours over two days.

The incident and two others that followed led President Fidel Castro to crack down on hijackings and accuse the United States of encouraging illegal immigration. In April, three Cubans who hijacked a ferry in a failed bid to reach the United States were executed.

This case was viewed as a test of the United States' commitment to aggressively prosecute hijackers no matter which country they come from. The presiding judge, James Lawrence King of Federal District Court, ruled last month that defense lawyers could not refer to Cuba's political or economic conditions.

Cuban exile leaders had argued that the United States should be lenient with the defendants because they were seeking freedom. Under the "wet foot, dry foot" policy, Cubans who arrive on American soil can stay in the United States. Those intercepted en route are returned.

Exile groups want the Bush administration to ease its policy, and were critical of a White House decision to return 12 Cubans suspected of hijacking a government boat in July.

Prosecutors said that the six men had worked for more than a year to develop a plan to overwhelm the crew and passengers of an old DC-3 by force, intimidation and threats. The men scouted the route and choreographed their actions, prosecutors said. Minutes into the flight to Havana, they charged the cockpit and broke down the door.

All the defendants confessed to the hijacking, but three confessions were rejected because F.B.I. agents did not read the men their Miranda rights.

In the last trial in the United States for hijacking a commercial plane, in 1997, three Cubans were acquitted of seizing a plane that ran out of fuel and crashed near Fort Myers.

Kirk Semple contributed reporting from New York for this article.