DALLAS (AP) — American Airlines put an unspecified number of employees on leave for their involvement in an incident in which several Black passengers were removed from a flight in Phoenix, allegedly over a complaint about body odor.

American CEO Robert Isom wrote in a note to staff that the incident was unacceptable.

“I am incredibly disappointed by what happened on that flight and the breakdown of our procedures,” Isom said in the note this week. “It contradicts our values. … We fell short of our commitments and failed our customers in this incident.”

Three Black passengers sued the airline last month, charging that they were removed from the January flight because of racial discrimination. They said they were told that a white male flight attendant had complained about an unidentified passenger’s body odor.

The men said they did not know each other and were seated separately while waiting for the plane to depart for New York. The three said they were among eight passengers – all the Black men on the flight, they said – who were told to leave the plane.

The men said they demanded an explanation for their removal during a confrontation with airline personnel in the jet bridge. At least one of the men recorded the discussion, capturing an airline employee seeming to agree that the men were discriminated against, according to their lawsuit.

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After a delay of about an hour, they were allowed back on the plane.

American did not say how many employees were put on leave or describe their job titles. A spokesperson for the airline said, “We are holding those involved accountable, including removing team members from service.”

Isom said American would form an advisory group to focus on the experience of Black customers, to promote the reporting of discrimination allegations, and to improve diversity training to “focus on real-world situations to help recognize and address bias and discrimination.”

In his note, which was reported earlier by CBS News, Isom said he had spoken with the president of the NAACP about the incident. The civil rights group did not immediately respond to a request for comment Thursday.

American has faced allegations of discrimination in the recent past. In 2017, the NAACP warned Black travelers about flying on the airline, claiming that several African American passengers had experienced discrimination from airline employees. American promised to make changes, and the NAACP lifted the advisory nearly nine months later.