Federal authorities on Thursday arrested a mechanic for American Airlines on suspicion of tampering with the navigation equipment on a Boeing 737-800 shortly before it was scheduled to depart with 150 passengers aboard. The Miami-to-Nassau flight was grounded just before takeoff in July, authorities said.

The mechanic, Abdul-Majeed Marouf Ahmed Alani, was upset that contract negotiations between his union and the airline had stalled, and he wanted to delay the flight with the hopes that he would make overtime pay, federal prosecutors allege.

According to federal investigators, Alani inserted and glued a piece of foam into the air data module system on American Airlines Flight 2834 on July 17, preventing it from functioning normally. The system, which sits beneath the cockpit, is responsible for monitoring an aircraft’s speed, pitch and other flight data.

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Crew members in the cockpit received an error message just as the Boeing 737-800 was approaching the runway and decided to abort the takeoff, authorities said.

“Alani stated that his intention was not to cause harm to the aircraft or its passengers,” said a criminal complaint affidavit filed in federal court in Miami. “Alani explained to law enforcement that he was upset at the stalled contract dispute between the union workers and American Airlines, and that this dispute had affected him financially. Alani claimed that he tampered with the target aircraft in order to cause a delay or have the flight canceled in anticipation of obtaining overtime work.”

Alani is expected to appear Friday in federal court in Miami. It is not immediately clear whether he has an attorney. Alani, who joined American Airlines in 1988, has been suspended, a company spokesman said.

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The 12,000-member mechanics’ union to which Alani belongs, the TWU-IAM Association, has been trying to secure a new contract with American Airlines for three years, The Associated Press reported. The company, which recently apologized to investors for various problems, has accused the union of purposely slowing down work, causing hundreds of flights to be canceled over the summer.

In June, American had a 4 percent flight-cancellation rate. the highest among U.S. carriers, and nearly seven times the cancellation rate of Delta Air Lines.

“We’re behind,” airline President Robert Isom said earlier this week. “We certainly haven’t produced the kind of margins and earnings that we had hoped. We haven’t run the best airline in our history.”

The airline said it would resume negotiations with the mechanics’ union on Sept. 16 with the help of a federal mediator, the AP wrote.

After the July incident, the Boeing 737-800 was taken out of service and sent for maintenance, which was when the foam was discovered, The Miami Herald reported.

“American immediately notified federal law enforcement, who took over the investigation with our full cooperation,” American Airlines spokesman Ross Feinstein said in an email. “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.”

Passengers on Flight 2834 were put on a different plane, which then took them to Nassau, the airline said. The air data module system has been fixed on the original plane, which has returned to service.