When I was flying I tried to limit my intake of salt. Very hard to do with airport food being like all fast food and loaded with salt. Avoid the hotel vending machine and packaged nuts/pretzels during flights. I think what's also as bad is all the soda you end up drinking since it's free during the flight and the caffeine a good kickstart on early showtimes.

I actually found not eating while cruising helped the most. Because our tastebuds are not as sensitive at altitude those little salt/pepper packets add flavor to the food your eating. Which if your trying to cut salt are that much worse since you can barely taste the salt you just dumped on your meal.

Probably packing your food is the best way to go.