Your Dog's Safety Under the PlaneThe biggest safety hazards to dogs under the plane come from extreme temperatures and poor ventilation. Although most major commercial airlines actually have temperature-controlled cargo holds for the flight itself, they don't activate when the plane is on the ground.
Where do dogs go under the plane?
Pets are placed in “hold 5”, at the rear of the plane. It is part of the cargo area underneath the cabin, but it is separated and it is heated. It is kept at the same temperature and pressure as the cabin, since the captain is notified of animals on board, and will make sure of this.