OAKLAND (CBS SF) — California Women’s head basketball Lindsay Gottlieb was confronted at the Denver airport by a Southwest Airlines employee who questioned her relationship to her infant bi-racial son before she could board a flight.

Gottlieb took to Twitter Sunday night to file a series of posts complaining about her treatment.

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“I’m appalled that after approx 50 times flying with my 1-year-old son ticket counter personnel told me that I had to “prove” that he was my son despite having his passport,” she tweeted in one post. “She said we have a different last name. My guess is because he has a different skin color.”

Gottlieb gave birth to Jordan Peter Martin — whose father is African-American — on May 7, 2017. The little boy traveled often — flying Southwest at times — with the Cal basketball team this past season.

Cal women's basketball coach Lindsay Gottlieb and her family. (CBS)

Cal women’s basketball coach Lindsay Gottlieb and her family. (CBS)

The Cal coach tweeted that after showing the ticket personnel Jordan’s passport — she asked to see a Facebook post to further verify her parentage.

“She 1st asked for proof with a birth certificate,” Gottlieb tweeted. “She then said it was a ‘federal law’ but asked me to prove I was the mother with a Facebook post. What?? The mother next to me said she’s never been asked for proof diff last name…not shockingly, not mixed face family.”

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“I do feel like as a white female, with a position of privilege, and a platform where someone is going to listen, it is my responsibility to say, hey, this happened, this isn’t okay,” Gottlieb said in an interview with KPIX 5. “And maybe somewhere down the line, that helps my son, who is bi-racial and will be for his entire life.”

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In a statement to KPIX 5, Southwest apologized and said it was launching an investigation into the incident.

“We’re looking into this specific interaction, and we have engaged with the customer directly to address her concerns,” the statement read. “Our employees are well regarded for their hospitality and we always strive for the best experience for anyone who entrusts us with their travel.”

Gottlieb said she did not believe it reflected the attitude of the airline.

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“I suspect it was just one insensitive employee,” she said. “It hurt my feelings. It made me feel a little bit less than and it’s not okay.”