DALLAS — A Southwest Airlines flight attendant was assaulted by a passenger and lost two teeth in the attack last weekend, according to a union president, who complained to the airline’s CEO about unruly passengers.

“Unfortunately, this is just one of many occurrences,” said the union president, Lyn Montgomery. She said there were 477 incidents of “misconduct” by passengers on Southwest planes between April 8 and May 15.

Montgomery did not provide details about the assault in the letter she sent Monday to Southwest CEO Gary Kelly. The airline did not immediately respond to a request for comment.

The Federal Aviation Administration said Monday that airlines have reported 2,500 incidents of unruly passengers this year, including 1,900 cases in which passengers refused to wear face masks, which are required by federal rule. The FAA provided those numbers as it announced it was seeking civil penalties totaling $54,500 against five passengers for behavior ranging from refusing to wear a mask to assaulting flight attendants.

Montgomery asked the Southwest CEO to lobby for putting more federal air marshals on flights and to ban passengers who violate rules instead of putting them on another flight. She said flight attendants are concerned about Southwest resuming sale of alcohol on board planes. Many recent cases that have caught FAA’s attention involving passengers who were drinking.