Downtown Loner Admits Threatening Airliners : Crime: Authorities suspect that the man, a welfare recipient living in a low-cost hotel, made more than 300 bogus calls in nine years.

The calls were all empty threats, placed from pay phones throughout the country by a shrill-voiced man who warned that bombs had been smuggled aboard airplanes or that planes were about to be hijacked.

“Listen very carefully! This is very important!” the excited man shouted. “An explosive device has been planted aboard your 12:05 p.m. flight from San Francisco to Toyko! I repeat! The bomb is an automatic device!”

And, in another call: “A man aboard the flight from San Diego to San Francisco is going to try to hijack the airliner. He’s carrying a flammable flask with flammable liquid. The person is very dangerous and violent! You must stop him! He has boarded the flight!”

The caller was William Albert Risley, a 50-year-old loner and welfare recipient who, until his arrest a year ago, was living in obscurity in a $15-a-night downtown San Diego hotel.

On Tuesday, Risley pleaded guilty to six felony charges of endangering the safety of aircraft in flight. In return, the federal government agreed to drop its investigation into his past.

Over the past nine years, authorities believe, Risley has called in more than 300 fake threats to the airlines, from public phones in San Diego, San Francisco, Detroit and Washington.

Officials estimate that his pranks have cost the airline industry more than $1 million as frantic pilots rerouted their flights or hurried back to airports, and as extensive ground inspections were conducted on runways.

The motive of Risley, a small, wiry man, is something that escapes even his family and defense attorney.

“I have no idea why he did this,” said his mother, Geraldine Rubenstein, in a telephone interview from her home in Oklahoma City.

“He never disliked the airlines--absolutely not,” she said. “He was never, ever diagnosed as having mental problems. I think he is just a loner.”

Defense attorney Steve Hoffman added: “Who knows why a person does this?”

Although Hoffman acknowledges that his client made “quite a lot of the calls, probably over 100,” he is not as sure that more than 300 threats were made.

But, he added, “We may never know that for sure, either.”

The problem of such bogus threats was addressed on a national level just last week, when James Busey, administrator of the Federal Aviation Administration, said the agency is “taking steps” toward installing telephone tracking devices at FAA facilities. He said about 600 bomb threats a year are phoned in to U.S. airlines and airports.

William Jackman, a spokesman for the Air Transport Assn., confirmed in a telephone interview Tuesday from Washington that prosecutors are correct when they say Risley’s prank calls cost the airlines more than $1 million.

“If it took rerouting of airplanes and changing of equipment, it could be that high,” he said. “When all the national hijacking started, we did an analysis and found it costs us $10,000 just to go to Cuba and land and come right back. And that was 20 years ago.”

More important to Assistant U.S. Atty. Larry Burns, the prosecutor who brought the case against Risley, is the danger to an airplane crew and passengers when a bomb threat is phoned in, regardless of whether it is bona fide.

“This guy is especially dangerous to an industry that relies on trust,” Burns said. “Imagine your frame of mind if you’re the pilot. Imagine your distress if you hear there’s a bomb on board.

“It’s a highly volatile situation, and a pilot under that kind of stress trying to land a plane is likely to be more concerned about getting the plane down quickly to the ground than he is about ordinary safe-landing procedures.”

The prosecutor also noted the precarious position for the airlines, which must react instantaneously to the threats.

“They’re damned if they do and damned if they don’t,” Burns said. “But imagine if they didn’t take appropriate action, and the bomb blew up in the air. Imagine the field day attorneys for the victims’ families would have with that. What jury isn’t going to award Ft. Knox in a case like that?”

In Risley’s case, Burns and FBI Agent Samuel N. Stanton gathered enough evidence to show a pattern in which the former graphics artist repeatedly used pay telephone booths to call the airlines and airports.

In at the federal courthouse, which officials said were authenticated by a speech expert as being of Risley’s voice, the agitated man can be heard screaming and shouting about bombs in luggage, “wacko women” with firearms intent on hijacking planes, and even a vigilante group called the People’s Ad Hoc Committee to Stop the Airport Construction.

“She wants to get back to Central America!” he yelled at one airline registration agent.

“She doesn’t know what she’s doing! She’s dark-complected! Dark hair! You must do something! She’s going to hijack the airliner! She has some kind of weapon!”

The events leading to Risley’s arrest in San Diego began with a threatening phone call in December 1988 to American Airlines.

“This is an emergency, listen carefully!” the caller warned. “There is an electronic bomb device on your 11:35 flight to Dallas-Ft. Worth from San Diego.” The airline reservations clerk said, “Excuse me?” and the caller hung up.

About 20 more calls were made in the following months to airlines operating at Lindbergh Field. Each time, the voice was nasal-sounding and effeminate, and the caller, believed to be a white man between 40 and 50 years old, spoke with a speech impediment.

One call was made to Harbor Police at Lindbergh, and a tracing device was placed on the Harbor Police phone line.

Stanton, the FBI agent, learned that 88 similar telephone bomb threats were made between October 1987 and May 1988 to airlines at San Francisco International Airport. Many calls were also made to Detroit Metropolitan Airport in earlier years.

In March 1989, the Harbor Police line that was being monitored received another threatening call. “Take this call very seriously!” the man said. “There is an explosive device on board a 4:20 p.m. flight from San Diego to Salt Lake City! It is in the baggage of the airplane!”

The call was traced to a public phone at San Diego Physicians & Surgeons Hospital. Stanton, in an affidavit filed in court, described how he learned that Risley had been an outpatient at the hospital at that time, and that he was a welfare recipient who had lived in San Francisco and Detroit when the calls were made there.

Stanton also said in his affidavit that Risley had moved into the Golden West Hotel in San Diego about the time the fake calls began here.

The agent said he later followed Risley back to the hospital, where he made another call from a pay phone. “While placing this telephone call,” the affidavit said, “Mr. Risley was observed to be looking around nervously.”

He said the call was to an Alaska Airlines reservations center in Long Beach. “There is a bomb on the 5:45 plane leaving San Diego to Portland,” the caller said, according to the affidavit. “I mean 5:45 p.m. plane from San Diego to Seattle. It is an explosive device.”

Risley later was arrested, and authorities said they found airline and Lindbergh Field schedules in his pockets.

His guilty plea Tuesday represents his first conviction, although officials said he has been arrested half a dozen times since 1957, for such offenses as robbing and mugging a homosexual, assault and battery and using a pencil as a deadly weapon. The records show that all of those cases were dismissed.

He is scheduled to be sentenced on the bomb threat charges July 2, when prosecutors plan to ask U. S. District Judge J. Lawrence Irving to impose a 10-year sentence, without parole.

His mother said she hopes defense attorney Hoffman can persuade the judge to levy a two- to three-year sentence.

“It breaks my heart that I may not even be alive when he gets out,” she said of her son. “He was always a very nice young boy, and as a young child and a teen-ager and so forth, he wouldn’t have anything to do with anybody who got in trouble. It’s not drugs. He’s never been involved in drugs.

“He was always a very nice boy. But sometimes life is so hard, it makes us do some crazy things.”