Eighty African American and minority ramp workers employed by American Airlines in Philadelphia and Washington have asked U.S. Attorney General Loretta Lynch to investigate American for alleged racial discrimination, safety and workplace violations, and removal of faulty airline equipment during a federal investigation.

The workers, who load and unload baggage and cargo from planes and operate trucks and heavy equipment on the tarmac, sent a complaint letter Tuesday, asking Lynch to look into maintenance improprieties, as well as workplace racism.

In January, Transport Workers Union Local 591 sued American over maintenance practices by mechanics in Dallas-Fort Worth and Chicago O'Hare, alleging that managers were pressuring mechanics to send out airplanes that needed repairs and were unsafe.

A federal judge in Chicago dismissed the lawsuit last month.

The ramp workers' complaint letter bypassed their union, the International Association of Machinists and Aerospace Workers. "This is the first I am hearing of this," IAM spokesman James Carlson said Wednesday.

In response, American said Wednesday that the safety of customers and employees "is our highest priority" and that the airline's training procedures and equipment are "the best in the industry and fully comply with government safety regulations."

"When it comes to racial discrimination, we conducted a thorough investigation," American spokesman Casey Norton said. "It included extensive interviews with employees and managers, and there is no evidence to support these claims."

In 2010, the ramp workers' Philadelphia lawyer, Brian R. Mildenberg, sued US Airways on behalf of the NAACP for alleged discrimination against African American employees at Philadelphia International Airport. The case ended with an undisclosed settlement and a pledge by the airport's largest airline to improve workplace diversity.

American and merger partner US Airways employ 8,000 in Philadelphia.

In September, Mildenberg filed safety complaints with the Federation Aviation Administration and the Labor Department's Occupational Safety and Health Administration (OSHA), alleging the use of unsafe and faulty airline ground equipment, including baggage tugs and trucks with defective brakes, bent and rusted wheel axles, missing horns and broken headlights, defective exhaust systems, and broken driver and passenger seats.

In January, the FAA's Flight Standards Service "substantiated that a violation of an order, regulation, or standard related to air carrier safety occurred" at Philadelphia. The FAA letter said the agency would take "appropriate corrective and/or enforcement action." The FAA did not specify what the violation was.

OSHA, after an inspection last fall at Philadelphia airport, fined American $11,000 in March for five workplace hazards that ranged from employees operating industrial trucks without proper nameplates to "excess and pooled motor oil" in a terminal baggage handling area that could cause workers to slip and fall.

In this week's complaint, the ramp workers asserted that faulty trucks and equipment were removed from Philadelphia airport and put in North Philadelphia before the FAA and OSHA inspections to hide it "from the eyes of federal inspectors."

The letter cited an unidentified American engine mechanic who claimed that managers were pressuring maintenance mechanics to omit steps in repairing engines, and allow planes that needed repairs to fly.

The workers said alleged workplace discrimination included racial slurs by managers, offensive nicknames for jobs and parts of the terminal, and segregation within break rooms, control rooms, teams, and job assignments.