A black transgender journalist has claimed she was kicked off a United flight for wearing an upside-down American flag T-shirt and a Black Panther superhero hat.

Amanda Stevens was preparing to board her flight from Albany to Chicago on Wednesday when she said a United representative first raised concerns about her outfit.

Stevens said she was told that her shirt, from New York rapper A$AP Rocky's discontinued PacSun line, made the flight's pilot "uncomfortable".

"I was grumbling because I was frustrated."

Stevens said she was then told that she could not wear her hat, designed with the logo for the Marvel superhero character Black Panther.

"This is unreal and f*****g racist", Stevens wrote on Twitter.

"The pilot feels 'uncomfortable' @united I didn't know he has to look at me while he flies. I feel uncomfortable havin a racist pilot," she added.

Stevens also claimed the pilot 'didn't seem that bothered' as he gave her a "smug look" when he walked past her on the way to the bathroom.

The journalist then revealed on Twitter she had been kicked off the flight.

Stevens said that United officials told her the exchange with the flight attendant was the reason she was being removed from the plane.

She returned to the airline's service counter at the gate after receiving a direct message on Twitter from the official United account, expecting to receive a seat on the next flight.

But Stevens said she was not acknowledged for more than two hours, adding that the attendant who was involved in the incident stayed in an employees-only area.

Three hours after Stevens first tweeted about the conflict, she told her followers she was "safe and sound" on a new flight.

"Thanks for the support," she also wrote. "F**k the hate. I just want to be in Chicago focused on work."

This isn't the first time the upside-down flag shirt that Stevens wore has stirred up controversy.

PacSun pulled A$AP Rocky's shirt from stores in May 2015 after many took to social media to express that they found it offensive and planned to boycott the store.

According to the United States Flag code, the upside-down flag is only meant to be displayed as a signal of "dire distress in instances of extreme danger to life or property".

The California-based retailer said in a statement that it decided to pull the shirt "out of respect for those who have put their lives on the line for our country".

A$AP Rocky has frequently used the upside-down flag as a symbol in his performances and clothes.

He has said in concerts that the upside-down flag "represents the war we're fighting".

"The reason that those flags are upside down are because our world is upside down," he said during one 2012 performance.

"We're just trying to be understood," he added.

Stevens has worn the shirt on flights before, but said she had turned it inside out.

A number of Twitter users rallied to Stevens' defense on Wednesday, with some sharing similar experiences.

"I'm sorry you're going through this unreal #racism," one person wrote. "I've been through similar for havin an Arabic tattoo."

David Blair wrote to Stevens that he was in the middle of booking a United flight when he saw her story.

"American Airlines got my money instead," he tweeted.

"I wonder if people with confederate flag hats get grief as well," another user tweeted at Stevens. "Spoiler alert: They probably don't."

United sent an official statement regarding the incident to io9, but mixed up Stevens' complaint with another woman from two weeks ago.

"We have reached out to Ms Campos to discuss her concerns," the statement read.

"Our goal is to provide safe and comfortable travel for all of our customers and we regret that Ms Campos was unhappy with the handling of the seat assignments on her flight."

"United holds our employees to the highest standards of professionalism and has zero tolerance for discrimination."

The statement was actually in reference to Mary Campos, who was forced to change her seat on a United flight after two Pakistani monks told the airline they could not sit next to a female.

Campos wrote a complaint to United's CEO and said she had been a victim of discrimination.

After io9 pointed out the mistake, United released a second statement saying the airline was "in contact with Ms Stevens to discuss this matter further".

"Both United and SkyWest hold our employees to the highest standards of professionalism," it added, "and have zero tolerance for discrimination."