Though he recommended courts-martial for two aviators whose plane clipped a ski gondola cable and killed 20 people, a military judge says the outcome of any trial isn't certain.

Lt. Col. Ronald Rodgers recommended trials for the pilot and navigator of the Marine EA-6B Prowler involved in the Feb. 3 accident. He also said charges against two backseat crewmen should be dropped.Yet in the summary of his report, obtained Thursday by The Associated Press, Rodgers said the outcome of the pilot's trial is in "substantial doubt."

The pilot, Capt. Richard Ashby, 30, of Mission Viejo, Calif., was recommended for court-martial on charges of involuntary manslaughter, negligent homicide, damage to military property, damage to private property and dereliction of duty.

The navigator, Capt. Joseph Schweitzer, 30, of Westbury, N.Y., was recommended for trial on charges of negligent homicide, damage to military property and dereliction of duty.

Lt. Gen. Peter Pace, commander of Marine Forces Atlantic, is expected to decide whether to order the courts-martial later this month.

Rodgers, who presided over investigative hearings in May and June, said in his report there was doubt about the outcome of Ashby's case because of "systemic errors for which none of the mishap crew can be held accountable."

Defense lawyers argued during the hearings that the cable wasn't marked on charts of the area around the Aviano, Italy, air base where the Prowler was based for missions over Bosnia. Information about altitude restrictions for the area also was confusing, they said - the U.S. minimum altitude was 1,000 feet and the Italian minimum was 2,000 feet.

To win a conviction against Schweitzer, prosecutors must offer expert testimony indicating his performance was "seriously deficient" in not calling for Ashby to slow down and climb.

"It may be that the government has such evidence in its arsenal; however, it was not offered for my review," Rodgers wrote.