An Australian model who avoided jail in the US after fighting with a flight crew has been detained by immigration authorities since September after her visa was revoked.

Former Miss Australia finalist Adau Mornyang faced up to 21 years jail after being found guilty in March of slapping a flight attendant during a foul-mouthed rant on a United Airlines flight in January.

A Los Angeles court sentenced her in July to 100 hours community service and placed her on three years’ probation.

But on September 17, Mornyang was reportedly arrested and jailed in a “surprise ambush” by US immigration and customs enforcement officials.

According to her sister Maria, it was claimed Mornyang was in the country illegally. She has been detained since and is being held “indefinitely” in an immigration detention facility.

“Adau was shocked, since she knew she never entered the United States illegally nor overstayed her visa,” Maria wrote on a Go Fund Me page launched on November 28.

The page aims to raise funds for Mornyang’s legal fees.

A Department of Foreign Affairs and Trade spokesperson confirmed the department is “providing consular assistance to an Australian detained in the US.”

The spokesperson would not comment further because of privacy obligations.

Formerly a prolific social media user, Mornyang has not posted to her Instagram page since September 2, when she spoke of “new beginnings.”

https://www.instagram.com/p/B14dcGWhe5c/

During the flight from Melbourne to Los Angeles, Mornyang launched a rampage that included calling a flight attendant a ‘white trash bitch’ when she was refused alcohol service.

A jury heard Mornyang ordered “several glasses of wine'” and passengers complained about her disruptive behaviour nine hours into the flight.

She he began “yelling obscenities and racial slurs and flailing her arms”, prosecutors said in their sentencing memorandum.

The court heard a flight attendant who approached Mornyang was slapped on the face before the model locked herself in a bathroom.

An air marshall eventually handcuffed her and held her at the back of the plane.

She accused the attendants of racism, told one she is “ready for your white ass” and threw her socks at another passenger.

“I am a human being who made a terrible mistake,” Mornyang told the court in July during a hearing.

The 25-year-old, who came to Australia from South Sudan as a 10-year-old refugee, said at the time of the flight she was self-medicating for anxiety and depression brought on by childhood trauma.

Mornyang was convicted of felony interference with a flight crew and misdemeanour assault.

In sentencing her, US District judge Cormac J Carney cited her “tragic history” of sexual and physical abuse and alcoholism for his leniency.

Prosecutors had wanted Mornyang to be jailed for a month.

“I have severe depression,” Adau Mornyang posted in August. Photo: Instagram

The Go Fund Me page claims US immigration agents revoked Mornyang’s visa without notice in retaliation for escaping prison.

“This no-jail outcome must’ve infuriated [immigration] officials who proceeded (without Adau’s knowledge) to revoke her valid visa and subsequently arrested her for being in the country illegally,” it says.

Mornyang’s US visa, as provided by sister Maria Mornyang. Photo: Go Fund Me

“Meanwhile, a judge never ordered that Adau should leave the country.

“My sister has been in jail for over two months, she’s not been given any trial since arrest by [US immigration] nor found guilty of overstaying her visa, just kept in jail indefinitely.”

Mornyang “expected that she was going to be deported after her arrest on September 17, 2019,” Maria said.

“That didn’t happen either.”

Maria says Mornyang’s visa for people with ‘extraordinary ability’ is valid until December 26, 2021.