(CNN) -- A fired United Airlines flight attendant plans to admit in court that he made eight bomb threats against his former airline.
Patrick Cau, 40, a German citizen living in Los Angeles, was arrested in January while training for a flight attendant job at another airline -- American.
Although the threats received widespread attention at the time, news of his arrest and the charges are just coming to light now.
In a plea agreement with federal prosecutors, Cau admitted to making eight bomb threats between Oct. 4, 2012, and January 2, 2013, from pay phones in Los Angeles, New York City, Las Vegas and Seattle. In each case, the caller claimed explosives had been placed on United flights.
The threats disrupted law enforcement and inconvenienced passengers, according to the court filing.
Each time, officials evacuated planes, re-screened passengers and searched bags and cargo, but did not find explosives.
Cau's attorneys, John Duran and Craig Charles, said he worked at United for 15 years as a purser, or flight attendant supervisor.
Cau filed a sexual harassment complaint against a male supervisor and was dissatisfied with how the carrier handled it, Duran said.
After lodging the complaint, the airline fired Cau for an incident involving a passenger, Duran said.
But Cau believed the firing was retaliation for his complaint.
Duran and Charles declined to say how authorities came to believe Cau was responsible for the bomb threats or when the investigation began, but said authorities have a circumstantial case.
They confirmed that many of the threats involved Cau's old London to Los Angeles route.
He has agreed to plead guilty to one count relating to false information and hoaxes next Monday, according to the agreement filed in Los Angeles. The charge carries up to five years in jail.
Duran said Cau had no previous criminal record, so American would have had no reason not to hire him when he applied for a flight attendant job.
But when American conducted a records check before a training flight, it discovered Cau was on a no-fly list, Charles said. The FBI arrested him at an American training center.
Both airlines confirmed they once employed Cau but declined further comment.
Charles described Cau's legal situation as "delicate," acknowledging that he had signed a plea agreement, but saying "as of today (he had) not officially admitted in open court to any of the allegations."