(CNN) — An emotional-support dog bit an American Airlines flight attendant Monday, resulting in an injury that required five stitches.

The incident occurred on Flight 3506 from Dallas to Greensboro, North Carolina, operated by partner Envoy Air, American Airlines said.

Medical personnel examined the attendant when the plane arrived. He did not require treatment and was cleared to return to Dallas/Fort Worth, where he received five stitches, the airline said.

American Airlines did not say what type of dog was involved.

The Association of Flight Attendants called for the Department of Transportation to prevent Monday's incident from repeating.

"What happened on yesterday's American Airlines flight is completely unacceptable and inexcusable," the flight attendant union said in a Tuesday statement . "For years, AFA has supported the role trained animals can provide to passengers in the cabin, but we have also called for action in regards to setting standards for emotional support animals."

American Airlines last updated its emotional-support animal policy in March. For service animals, the airline permits dogs, cats and miniature horses. Emotional-support animals must be dogs or cats.