DENVER — Southwest Airlines asked a woman to prove her relation to her biracial son while they were at the Denver airport on May 28, the BBC reports.

Lindsay Gottlieb, who is white, was traveling with her African American fiance Patrick Martin and their son, when they showed the official their child's passport at the airport.

However, the official asked for further evidence to prove they were a biological family, asking to see a Facebook post or a birth certificate.

Gottlieb said "being pushed further to 'prove' that the child was her son felt disrespectful," the Washington Post reports.

Gottlieb claimed in a tweet that she has flown with her son "approximately 50 times," and this type of an incident has never occurred.

The airline was quick to apologize in a statement and said they were going to launch an investigation into the incident, CBS News reports.

Gottlieb claims the officials told her that the airlines would treat the incident as a "coaching" moment for their employees, referring to Gottlieb who coaches the Women's basketball team at the University of California at Berkeley, CBS News reports.