The man's attorney said that United had declined to investigate the man's claims that a male supervisor sexually harassed him.
A United spokeswoman confirmed that the man had worked for the airline but declined to comment further. The man had been hired by American Airlines to become a flight attendant shortly before he was arrested.
According to court documents, Patrick Cau used pay phones near his Los Angeles home and around the country to make threats against six United flights between last October and January. One call went to a United crew-scheduling number, the others to 911.
Under an agreement filed last week in federal district court in Los Angeles, Cau will plead guilty to one count of making a bomb threat against a plane. Cau, who also goes by the name Patrick Kaiser, is expected to enter a plea Monday and be sentenced this fall.
The felony charge carries a maximum sentence of five years in prison and a fine of $250,000, although federal prosecutors agreed to recommend a lesser sentence. The U.S. Attorney's office in Los Angeles did not return calls for comment.
Cau agreed to pay restitution — United said it lost $267,912 because the flights were delayed or cancelled after the threats — and, as a German citizen, he also faces possible deportation.
His attorney, John Duran, said that Cau worked for United for 15 years and rose to the position of purser or head flight attendant. Duran said Cau filed a sexual-harassment case against a male supervisor, but the case "didn't go anywhere."
"There was an actual basis for his unhappiness with United," Duran said. "He's a good guy who made some really poor decisions."
Cau was indicted in May and remains in custody. Duran said his immigration status made him ineligible for bail.
In February, American accepted Cau into its training program for new flight attendants. He began training in March but was fired in April after his name appeared on a government no-fly list, said Matt Miller, a spokesman for American.
Miller said the company checked Cau's background for any criminal record and whether he was on the government's no-fly list, but nothing turned up.
"My understanding is he was added to the list after" the airline's background check, Miller said. "That was the first red flag."
A spokesman for the U.S. Terrorist Screening Center, which maintains the no-fly list, said the agency wouldn't say why or whether an individual is on the list.
Miller said Cau travelled on two flights during training and may have served drinks to passengers but would not have performed any duties related to safety or security.
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