A 24-year-old Australian woman is facing up to 21 years behind bars after being convicted of federal charges in an assault on a flight attendant during a trip from Melbourne to Los Angeles earlier this year, prosecutors said Monday.

Adau Akui Atem Mornyang, of Victoria, appeared to be intoxicated and was verbally and physically abusive to both staff and other passengers aboard a United Airlines flight on Jan. 21, the U.S. Attorney’s Office for the Central District of California said in a news release.

Evidence presented at trial indicated that, after being in the air several hours, other passengers complained to a flight attendant about Mornyang, who was flailing her arms and shouting obscenities and racial slurs, officials said.

When the attendant then approached Mornyang to check on her, the defendant allegedly yelled at him then slapped him across the face.

The flight attendant tried to restrain Mornyang until federal air marshals could respond. The marshals then had to stay with Mornyang in the plane’s rear galley for the rest of the trip, prosecutors said.

Last Thursday, a jury found Mornyang guilty of one felony count of interference with a flight crew and one misdemeanor count of assault.

She is scheduled to be sentenced June 24, when she’ll face a maximum possible penalty of 21 years in federal prison.