MIAMI (AP) _ A Cuban refugee accused of commandeering a jetliner 3 1/2 months ago was found innocent by reason of insanity today and ordered to undergo additional psychiatric tests.

Pedro Rene Comas Banos was scheduled to begin trial Monday on federal air piracy charges for attempting to divert a Miami-bound American Airlines flight to Cuba.

U.S. District Judge James W. Kehoe based his ruling on reports from two psychiatrists and a neurosurgeon who concluded Comas was ''insane at the time of his acts.''

After his court appearance, Comas, 38, was returned to the federal Metropolitan Correctional Center south of Miami, where he has been held since arrest by the FBI shortly after the May 27 incident ended.

Kehoe ordered additional mental tests for Comas. A Nov. 6 hearing was scheduled to receive reports and testimony on whether Comas should be freed or sent to a mental institution.

Comas was in mental facilities in Cuba before emigrating during the Mariel boatlift of the early 1980s, said assistant federal public defender Lori Barrist, who represented Comas.

Three of Comas' sisters, who live in Miami, also indicated their brother had history of mental illness, said Ms. Barrist.

The United States has long accused Cuban leader Fidel Castro of using the Mariel boatlift as an excuse to send prisoners and mental patients to the United States along with the thousands of law-abiding Cubans seeking to escape Castro's rule.

Comas boarded an American flight in Los Angeles and changed to a Miami- bound plane in Dallas on the ninth anniversary of his flight from Cuba.

As the aircraft neared Miami, he fired a shot from a pistol and threatened to blow up the jet with plastic explosives unless the flight was diverted to Cuba, said Assitant U.S. Attorney Marc Jimenez. Authorities later discovered Comas brandished a starter's pistol used in athletic events. The pistol was not discovered by detection devices in Los Angeles or Dallas.

Jimenez said the airline captain diverted the flight on a course to Havana but returned to Miami after deciding the plane did not have enough fuel.