In a scathing Facebook post that has been shared more than 20,000 times, she told on Sunday how the situation unfolded when the unwell passenger, who was sat just two rows in front of her, screamed for help.
She immediately jumped out of her seat to assist him but was slapped down by the stewardess who said he has simply suffered 'a night terror'.
Crew made an announcement asking for the help of a doctor moments later when the man's condition did not improve, but she was dismissed again.
"I raised my hand to grab her attention. She said to me "oh no sweetie put ur (sic) hand down, we are looking for actual physicians or nurses or some type of medical personnel, we don't have time to talk to you".
"I tried to inform her that I was a physician but I was continually cut off by condescending remarks."
"Then overhead they paged "any physician on board please press your button". I stare at her as I go to press my button.
"She said "oh wow you're an actual physician?" I reply yes. She said "let me see your credentials.
'What type of Doctor are you? Where do you work? Why were you in Detroit?" (Please remember this man is still in need of help and she is blocking my row from even standing up while bombarding me with questions)."
An older, white male doctor then approached, Dr Cross claimed, and she was overlooked.
The passenger, who had fainted, began to improve but she claimed staff still asked for her advice as to how to handle him before landing.
Afterwards, Cross claimed the stewardess apologised repeatedly and tried to soothe the situation by offering her free air miles.
"I don't want skymiles in exchange for blatant discrimination. Whether this was race, age, gender discrimination, it's not right,"she said.
Delta said it was investigating the incident in a statement issued today.
"Discrimination of any kind is never acceptable.
"We've been in contact with Dr. Cross and one of our senior leaders is reaching out to assure her that we're completing a full investigation,' a spokesman told DailyMail.com.
They would not give any detail as to whether the flight attendant involved had been disciplined.
Cross's post was shared thousands of times on social media and inundated with messages of support.