US airliner turned back after human heart left on board

A Southwest Airlines flight headed from Seattle to Dallas was turned back mid-flight after it was discovered that a human heart had been left on board, officials said Thursday.The plane had was over eastern Idaho -- around 600 miles (950 kilometers) into the journey -- when staff discovered the "life critical cargo shipment," meant for delivery back in a Seattle hospital after being transported from California."Once we realized the error we immediately worked to return to Seattle," airline spoke