I forgot to mention....you should buy a wrist digital blood pressure cuff that requires you to pump up a bulb to inflate. Electric ones make a ton of noise and you can best believe the chickens will begin to cluck....buy some cayenne liquid tincture incase he begins having chest pains or having a heart attack...having some PH strips (vaxa) wouldn't hurt either (vaxa has some PH pills also in case his PH dips too low)...monitoring his PH and BP at all times helps protect him while his body adjusts to it's new environment and food overseas.... ;)
The most important thing about flying whether you're healthy or have health issues is making sure you don't produce blood clots. The back of the knees and feet area are called "Blood Clot Farms".
If your Father, check with his doc, can take vitamin E mixed 400mg, that will take care of the blood clots. Be SURE to NOT drink acidic food or drinks while in flight.
Most folks with health issues have low PH. My PH dropped to 3.85. Anything below 4.0 is suppose to be incompatible with life so I thank my Lord for saving my life. What happens when your PH drops to low this irritates fibrin in the blood which is component of blood clotting.
For me I began throwing blood clots and yes I survived a heart attack. So drinking or eating acidic foods while in-flight is not wise. You will be aiding the formation of blood clots if your PH is already low.
Brig Alkaline water (volvic water is a good brand) with you on your flight and drink that beverage only! And...drink that the entire time overseas as well.
Hope this helps.
The flight in an aircraft will have absolutely no effect on his condition. Modern commercial aircraft are pressurized at levels that provide oxygen at levels that would not cause problems. Most are pressurized at 7,000 MSL, regardless of how high the aircraft flies, but the latest aircraft are pressurized to 5,000 MSL. If he can breath normally without supplemental oxygen on a daily basis, he won't need any on the aircraft. The only issue is him being away from medical care while on the aircraft, and frankly, there would be more of a problem if he were to take a vacation in a small town without an ambulance service. The only thing to remember, is that IF, in the remote possibility the aircraft depressurizes, an oxygen mask will fall from above. This will not activate unless it is PULLED DOWN. Don't sit up to put your face in the mask. Curiously, on modern airliners, the oxygen is provided by ignition of an individual burning "oxygen candle" in a fireproof container.
Normally I would say yes, but the fact that he's having a checkup every month gives me cause for concern. Why are they checking him so often?