A Miss Australia finalist could spend 21 years in an American jail after being found guilty of assaulting a flight attendant during a long-haul flight.

Adau Akui Atem Mornyang, 24, was on a United Airlines flight from her hometown of Melbourne to Los Angeles when she became disorderly after she was refused alcohol.

The Sudanese-born model lashed out at two United Airlines staff during the flight on January 21, and was verbally and physically abusive to staff and patrons.

She faces up to 21 years in prison after she was found guilty of assault and interference with flight crew.

Adau Akui Atem Mornyang was on a United Airlines flight from her hometown of Melbourne to Los Angeles when she became disorderly after she was refused alcohol

Several passengers were forced to complain to staff about Mornyang's disruptive behaviour

Several passengers were forced to complain to staff about Mornyang's disruptive behaviour about nine hours into the flight.

They said she was 'flailing her arms, and yelling obscenities and racial slurs', according to a release by the Department of Justice.

'When the flight attendant approached to assess the situation, Mornyang began to shout at the flight attendant and then slapped him across his face,' the court heard.

The 24-year-old Sudanese-born model lashed out at two United Airlines staff during the flight on January 21

'The flight attendant attempted to restrain Mornyang until federal air marshals could assist. The federal air marshals were forced to stay with Mornyang in the rear galley of the plane for the remainder of the flight.'

The former Miss Australia contender claims to have no recollection of the commotion.

'All I remember was waking up after sleeping for eight hours,' she said in a text message after the incident.

She claims to have mixed two glasses of wine with prescription pills to help her sleep, but attendants insist it was closer to five or six glasses before she was cut off.

She claims to have mixed two glasses of wine with prescription pills to help her sleep, but attendants insist it was closer to five or six glasses before she was cut off

Mornyang, who moved to Australia as a refugee when she was 10, said: 'I was so confused and begging and pleading for them to tell me what I did.

'I was ignored, I was in and out of consciousness, and was later locked up in federal prison still with no memory of what I was arrested for.

'This whole alleged slapping is a big shock to me and I cry every night wondering why I have no memory of it. How I could of done it while asleep,' she told The Herald Sun.

She said the accusations have ruined her burgeoning career, having just landed her biggest contract to date before she was arrested.

Mornyang has previously modelled for makeup giant Sephora, and recently walked in New York Fashion Week.

She is scheduled to be sentenced on June 24.