Get tested, eat right
Your objective should be to get the BG level down, not game the test.
The most effective method to start with is reducing carbohydrate intake. Sugar and grains (thus flour) are big contributors, but fruit juice and some vegetables are high as well. (You do need some carbohydrates. High-fiber ones are said to be good for diabetics, I suspect that’s mostly that they slow digestion thus absorption so minimize peaks of BG.)
Excercise is good for weight and general health, especially if sedentary such as during long flights. But I doubt it helps BG much.
(Beware that people tend to mush advice together, falling into the correlation trap. For example, there’s an obvious correlation between obesity and diabetes, but the root cause is over-eating – especially carbohydrates. Consume substantial amounts of donuts and sugared drinks and you will probably become fat and develop diabetes. Exercise a lot but maintain your diet and you’ll lose weight but I doubt your BG will go down. (Another correlation is that people who start to exercise will probably make other life style changes, that’s good but many people tend to attribute improvement to one thing and ignore the other changes.)
I’ll grant that you apparently are not real high, but you should consult with a good doctor, who can help you curb the trend.