Every day millions of people travel by plane. However, a small percentage of passengers go weak at the knees just thinking about flying.(1) ....... others suffer acute physical discomfort, which is mostly brought(2)............. by the change in air pressure. So what can be done to prevent problems? If you move about as often as(3)............, that is walk up and down the aisle, you(4) .........prevent sluggish circulation and stiff joints. In(5)..............of breathing difficulties, you will be able to ease the problem only if your oxygen intake before boarding. A good thirty-minute brisk walk should help. If you intend to fly, it would also be wise to follow some general advice. Firstly, if you suffer from any serious health problems, ask your doctor if it's safe for you to travel or not. If you have a medical condition, don't forget to bring your medicine(6)..........It has been suggested that if you can climb a dozen stairs without getting(7)..........of breath, it is safe for you to fly. Should you have a heavy cold or a bad cough, try to avoid flying.