Bruce Alexander was on a flight travelling from Texas to New Mexico when he leaned forward twice and grabbed the woman’s brest, according to documents filed at New Mexico’s US District Court.
The woman, who has not been named, told investigators she initially believed the first touch was accidental.
About 30 minutes later she said she felt the 49-year-old grope her again and rose from her seat.
She then “told the passenger behind her that she didn’t know why he thought it was ok [to touch her] and he needed to stop”.
A fellow passenger who witnessed the incident corroborated the woman’s story, the documents claim.
The woman was helped by a Southwest Airlines flight attendant, who found her a seat in a different section of the plane.
Mr Alexander was detained by police officers when the plane landed in Albuquerque.
After he was handcuffed he allegedly referenced Mr Trump’s comments about sexual assault.