ADM stands for air data module and it tracks the plane's speed, pitch and other data, according to The New York Times.
Officials said Alani didn't want to hurt the aircraft or passengers on board, rather, he was mad over a contract dispute between union workers and American Airlines, according to CNN.
The dispute, Alani told officers, cost him income, so he sabotaged the plane so he could get overtime working on it.
The issue was discovered when the plane was getting ready to take off. When pilots increased the engines' power, the ADM system had an error. The flight was aborted and the plane returned to the concourse. Mechanics found a loose tube that is supposed to be connected to the ADM. When they looked at it they found "what appeared to be a dark Styrofoam-type material," the complaint said, according to CNN.
American Airlines reported Alani to the FBI two days after the alleged incident, the Times reported.
Alani was arrested Thursday, the Miami Herald reported, and faces 20 years in prison if convicted, according to the Times.