Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 240; Flight Crew Total 5567
Flight Deck / Cabin / Aircraft Event Other / Unknown; Inflight Event / Encounter Bird / Animal
Air Traffic Control Provided Assistance; Flight Crew Returned To Departure Airport
Human Factors
Shortly after the sterile light came off; we received a call from the back. The flight attendant described a dog that was out of control. The Captain informed me of the situation. The dog was a large lab size dog.Only a few minutes passed before we got a second call from the back. The Captain gave me control of the aircraft; and ATC communications. After the call; the Captain informed me that the flight attendant was frantic; and the situation was getting worse. The dog's owner was apparently not in complete control of the animal. The passengers around the dog and the flight attendant were fearful for their safety.We discussed the situation; and began a phone patch with dispatch. A third call came from back (perhaps 2 minutes from last call.) We were leveling at FL250 (I think). The dog was out of control. The dog had attempted to bite passengers; and / or flight attendants. The Captain was managing the call to dispatch and the flight attendants. At some point the flight attendants were able to get the animal locked into one of the lavatories. At this point the comfort of our passengers had been compromised; and the safety of our passengers and or our crew was in jeopardy. The Captain and I discussed our options of continuing on [several hour-long] flight to [our destination]; returning to [our departure airport]; or diverting to another field. Dispatch; the Captain; and I concurred that the safest course of action was to return to [our departure airport].ATC informed us that they would be [giving us landing priority]. We would have [notified them] anyways due to possibility of overweight landing. After further planning; it was determined that we would be landing overweight. Dispatch contacted [Operations Control]; and sent the calculations for a safe overweight landing. We chose to land on the longest runway. No further incident.
First Officer of a large passenger transport reported a dog becoming uncontrollable in the cabin area; threatening the flight crew and passengers.