Lindsay Gottlieb claims that a Southwest Airlines employee at Denver Airport, in the US, demanded she prove she was the mother to her bi-racial son, one-year-old Jordan.

The basketball coach says she was travelling on flight 1808 from Denver to Oakland when the incident occurred.

The shocked flyer took to Twitter to share her fury, saying she was baffled as it was the first time she’d ever been asked such a question — despite travelling with her son regularly as part of her work.

She wrote in a series of tweets: “I’m appalled that after approximately 50 times flying with my one-year old son, ticket counter personnel told me I had to ‘prove’ that he was my son, despite having his passport.

“She said because we have different last name. My guess is because he has a different skin colour.”

Ms Gottlieb alleges the employee asked for her son’s birth certificate, before demanding she prove she’s a mother “with a Facebook post”.

“It was demeaning and insensitive, not to mention inefficient. Would have missed flight if it was not delayed. I would advise better training for employees to avoid this happening to others.”

When asked by a fellow Twitter user if she was OK, she responded: “It was wild, but, I fear, much more common for people that don’t look like me.”

There has been a mixed response to Ms Gottlieb’s tweets, with people pointing out that the airline needs to be on guard against human trafficking and the kidnapping of children.

Others sympathised, saying the same thing has happened to them.

Southwest Airlines apologised for the incident and told local network KPIX 5 that it is looking into it.

“We’re looking into this specific interaction, and we have engaged with the customer directly to address her concerns,” a Southwest Airlines spokesperson said.

“Our employees are well regarded for their hospitality and we always strive for the best experience for anyone who entrusts us with their travel.”