<<Disclaimer: Verify this information before applying it to your situation.>>

Even before going "GF", I seem to remember airline food as being
completely inedible.

I fly at least once per year (and used to fly at least 3-4 times a year
before eating gluten free) and have always brought my own foods.
Among the GF arsenal:

Trail Mixes (made myself: plain pumpkin seeds, sunflower seeds, peanuts,
raisins, dried cranberries, GF cereal flakes/puffs)

Fruit Leathers: Stretch Island makes a great product.  About the size of
a dollar bill, so it's great for carrying in your purse/pocket when
traveling and unsure of the next GF meal to be found.

Health Valley Rice Bars: Individually wrapped.  Also good for slipping
into a pocket for emergency foods.

Miso Cup Instant Soup Packets: A nice hot cup of soup, individually
servings, also good for carrying around for emergencies.

Other things I've taken with me (not the best choices for the return
trip-too perishable) Fresh fruit, cheese slices, GF pasta salads,
hard cooked eggs, peanut butter in small salad bar to go dressing
containers (about 2 oz size).  Everytime, seat mates comment on how they
wish they'd done the same as I.

My next step is to figure out how to smuggle in my own inflight movie!