question: My father had pneumonectomy (removal of his left lung) two year ago due to lung cancer. He is now 73 in good health. he is able to walk very easily for a hours, but he could not do chores. Stairs could also be a challenge for him. he is considering traveling on a commercial flight for about 15 to 18 hrs. Do you think he can do that with his condition. Would portable oxygen supply help in this case?