Question: when did pan am airlines go out of business
[{'answer': 'December 4 , 1991'}, {'provenance': [{'wikipedia_id': '81024', 'title': 'Pan American World Airways', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 692, 'bleu_score': 0.5150550328602841, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6034022555091992557}, 'section': 'Section::::Abstract.'}]}]