William Paul (AP)

The 19-year-old son of Sen. Rand Paul (R-Ky.) was charged with assaulting a flight attendant in addition to the previously reported underage drinking and disorderly conduct charges he faces following an incident on a Jan. 5 flight from Lexington, Ky. to Charlotte. 

The Charlotte Observer reported on the additional charge, "a misdemeanor assault on a female by aggressive physical force." It was not clear why the assault charge wasn't disclosed in the initial reports. 

Police said William Paul may have been served alcohol on the U.S. Airways flight. In a statement last week, Sen. Paul's office asked for privacy on the matter.