Probe of Officers Reported as Limited to Use of Planes : Military: Fellow Marines express surprise that one of the El Toro colonels committed suicide, apparently over the matter.

An investigation into two high-ranking officials at the Marine air base here has focused almost exclusively on their questionable use of military aircraft, a defense attorney said Thursday, prompting surprise among some service personnel that this would be enough to drive one of the officers to suicide.

Military sources stressed, however, that the number of flights taken by Marine Cols. Joseph E. Underwood and the late James E. Sabow was high enough to attract the attention of the Naval Investigative Service, which probes allegations of criminal wrongdoing.

Ordinarily, officials said the indiscriminate use of planes would be handled internally on the base, without the involvement of the Investigative Service, but the agency has been called into the El Toro investigation.

Earlier this month, the inquiry led to the suspension of both Underwood, formerly chief of staff at the El Toro base, and Sabow, an assistant chief responsible for air operations. Underwood allegedly used a Marine C-12 Beechcraft for out-of-state golfing excursions. Sabow’s responsibility included overseeing the use of the Beechcraft. He also allegedly used a plane for personal reasons, sources said.

Base officials have issued no formal statement on the nature of the probe, but they have confirmed that one is under way for “official misconduct.”

On Tuesday, Sabow, 51, a 28-year veteran of the corps, took his life with a shotgun, officials said. Funeral services are scheduled for today.

Personnel at the Marine Corps Air Station in El Toro, home of the 3rd Marine Aircraft Wing, and at other Southern California military bases remained in shock Thursday over the suicide of Sabow in apparent connection with the investigation.

“I’m more than a little amazed and devastated myself,” said Col. Alex Lancaster, an assistant chief of staff for logistics at El Toro. “It’s all bizarre to my way of thinking.”

Marine Maj. Walter Bansley, senior defense counsel at Camp Pendleton and the attorney for Underwood, declined Thursday to say how many trips by his client were in question or where he had gone. The military also has declined to provide such information.

Bansley defended Underwood’s conduct as aboveboard, saying that the colonel had taken the trips to put in flight hours and maintain his active status as a pilot.

The military has been probing allegations that Underwood used the Beechcraft to go on golfing outings to the East Coast, Nevada and elsewhere, but Bansley said that any golfing Underwood did at his destinations was incidental to the trip.

“Assuming this is a legitimate training mission, what he does once he gets there is certainly not unlawful,” Bansley said.

“It’s like if you go out on a business trip to Kansas City and you like baseball, so you go to see the Royals play while you’re there.”

Asked whether the allegations extend beyond the use of planes for golfing trips and personal reasons, Bansley said, “Absolutely not.” A military source also confirmed that, with the exception of some issues of expense reporting and management, the probe has focused almost exclusively on the single subject.

Times staff writer Nora Zamichow contributed to this story.