The American Airlines mechanic who was arrested and charged with sabotaging a plane has worked for the airline since 1988.

However, for about 10 years, he simultaneously worked for Alaska Airlines, court documents show.

He was fired in 2008 for a series of mistakes — and double dipping by clocking in to both jobs at the same time — some of which led to investigations by the FAA, according to court documents obtained by Business Insider from an unsuccessful discrimination suit the mechanic filed against Alaska Airlines.

The mechanic said he sabotaged the plane in July because of frustration over contract negotiations between his union and American Airlines, according to the criminal complaint filed against him.

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The American Airlines mechanic who was arrested and charged with sabotaging a plane this summer was fired from Alaska Airlines in 2008 after a series of missteps that led to several Federal Aviation Administration investigations, according to court documents obtained by Business Insider from an unsuccessful discrimination suit the mechanic filed against Alaska Airlines.

Abdul-Majeed Marouf Ahmed Alani was arrested by the FBI on Thursday morning and charged with deliberately sabotaging an American Airlines plane that was about to operate a flight from Miami to Nassau, Bahamas.

The criminal complaint filed against Alani said he was "upset" over stalled contract negotiations between the union representing the airline's mechanics — the TWU-IAM Association — and tampered with a sensor connecting to the plane's air data module, or ADM, on July 17. The pilots noted an error message from the ADM as they were positioning on the runway to takeoff and returned to the gate, authorities said in the complaint.

After his arrest, he said he was not trying to hurt anyone on board the plane or cause lasting damage to the aircraft, according to the criminal complaint, and was trying "to cause a delay or have the flight canceled in anticipation of obtaining overtime work."

Alani has worked for American Airlines since 1988 without any major performance or disciplinary issues, according to a source familiar with the matter.

Although he was working in Miami at the time he is suspected of sabotaging the plane, and when he was arrested on Thursday, he was previously based in California, according to public records and the discrimination lawsuit filed by Alani. The FBI described him in a statement to Business insider as a resident of Tracy, California, a town about 60 miles east of San Francisco, where he appears to have been previously based — it was unclear whether Alani had moved to the Florida area, or whether he was commuting for duty using employee travel benefits.

Court documents show that from 1998 to 2008, Alani was also employed by Alaska Airlines. The airline confirmed his dates of employment to Business Insider. He was fired from the airline in 2008 following a maintenance mistake after working there for about 10 years, according to the discrimination lawsuit he filed against Alaska Airlines.

Alaska Airlines also confirmed to Business Insider that Alani was an employee for several months in 1990.

He sued the airline in 2010, alleging he was discriminated against; the court found in favor of Alaska the following year.

During the lawsuit, numerous instances of mistakes by Alani were reported, starting about three years before his termination, according to the court documents viewed by Business Insider.

According to the court documents, the errors occurred between 2005 and 2008. During some of the incidents, he filed reports under a program called the Aviation Safety Action Program (ASAP), which allows employees to self-report safety-related issues and errors, according to court documents of the judge's decision in the lawsuit. ASAP reports can be submitted to the Event Review Committee, or ERC, which is made up of a union representative, an airline representative, and the FAA.

In 2005, Alani filed an ASAP report after he entered the wrong code into a maintenance tracking database, according to documents Alaska Airlines entered as evidence. The ERC sent Alani to a "Back-To-Basics" remedial training program, the documents say.

Also in 2005, he forgot to check required inspection items when finishing a repair, according to the documents. The ERC closed the report without any further action.

In 2007, Alani made a mistake when installing an altimeter, according to the court documents of the judgement, and he submitted an ASAP report and notified the FAA of the potential safety hazard. Afterward, Alani was given an oral warning and told to attend training sessions again, according to the court documents.

Also in 2007, he made a mistake while installing a pitot tube, a sensor that helps determine a plane's air speed, according to documents Alaska Airlines entered as evidence. The FAA launched an investigation, while the airline gave Alani a written warning, the documents say.

Again in 2007, Alani made a mistake when sending a broken part — a Heads-up Guidance System (HGS) — to a mechanic base in Seattle, leading to it being installed in an in-service aircraft, according to the court documents. He received another oral warning and was told that any additional incidents could lead to his termination, the court documents say.

In 2008, according to additional court documents from Alaska, Alani and another employee accidentally installed the wrong battery on a plane. Alani filed another ASAP report and was told that day that he would be suspended pending an internal investigation, according to the documents. Like with the pitot-tube incident, the FAA opened its own investigation, according to the documents, and two weeks later, Alani was fired.

When he was terminated, Alaska Airlines told Alani he was being discharged because of the battery incident, the HGS mistake, and the altimeter issue, the court documents say. Alaska also alleged during the lawsuit that while the airline was investigating the battery episode, the airline found at least three occasions in which Alani was clocked in at both Alaska and his other job at American Airlines.

Alani also had his avionics-technician certificate suspended by the FAA for 30 days after the investigation into the battery error, according to the court documents.

In the ruling against Alani in his discrimination suit, the judge wrote that Alani's performance while at Alaska was clearly below standards.

"Plaintiff has not proved that he was performing his job satisfactorily," he wrote.

"While it may be true that portions of the blame for the four events that preceded plaintiff's termination may be attributable to other employees, plaintiff is the clear-cut common denominator in all of the incidents," the judge added. "Serious mishaps clustered to plaintiff to an unusual extent."

Alaska Airlines said in a statement that Alani had been a technician for the company but declined to provide further details of his employment, saying that "Alaska does not comment on specific personnel matters of past and present employees."

In a statement on Thursday, American Airlines said it was cooperating with the federal government's investigation:

On July 17, flight 2834 from Miami to Nassau, Bahamas, returned to the gate due to a maintenance issue. Passengers boarded a new aircraft which then re-departed for Nassau. At American we have an unwavering commitment to the safety and security of our customers and team members and we are taking this matter very seriously. At the time of the incident, the aircraft was taken out of service, maintenance was performed and after an inspection to ensure it was safe the aircraft was returned to service. American immediately notified federal law enforcement who took over the investigation with our full cooperation.

If you are a current or former aircraft technician or airline empolyee and have opinions or experiences to share, email this author at dslotnick@businessinsider.com.