On Tuesday, Delta Air Lines announced that it will begin providing members of its flight crews diversity training after the airline received heavy criticism after an incident involving prejudice in October 2016.

According to FoxNews.com, officials from Delta stated that the diversity training became mandatory for all executives last year and around 23,000 flight attendants would go through the same training starting in Spring 2017.

The announcement comes after the airline received massive backlash for an incident where a black physician who came forward on a flight to assist an ill passenger was denied the opportunity because the stewardess didn’t think she was a real doctor.

Delta said that its decision to require its flight crews to attend the diversity training was moved up as a result of the incident involving Tamika Cross, the Houston-based gynecologist who was mistreated by attendants in October.

“As part of Delta’s ongoing diversity and inclusion efforts, the airline launched inclusion training four months ago for Delta leaders,” Delta Air Lines spokesman Brian Kruse. He also went on to say, “Cultural sensitivity training has long been part of Delta’s flight crew curriculum.”

Delta is the last of the four largest airlines in the United States to make diversity training mandatory. As for the other major airlines, American Airlines makes its employees attend refresher courses every two years, United Airlines requires all employees dealing with customers to receive the diversity training and Southwest Airlines has mandated that all new employees attend anti-discrimination and anti-harassment courses.

The announcement from Delta also comes after the U.S. Department of Transportation issued new regulations on how to not discriminate against passengers on the basis of race, color, national origin, religion, sex or ancestry in air travel.

In addition, the transportation department released a document for passengers informing them of their rights and their freedom from unlawful discrimination.

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