I can't remember the last time I actually had a meal on an airplane, and I fly fairly frequently. I'm so tired of pretzels, peanuts, and those horrible little packages of snack mix that I routinely refuse them. The airline staff looks at me like I'm nuts, but instead of highly processed, high sodium, bad tasting 'food', I bring my own healthy and good-tasting snacks. Here are my favorites:

1. Homemade trail mix tastes far better, and is much better nutritionally, than anything you get on an airplane. I mix a variety of nuts and seeds together with a handful of dried fruit (craisins are my current favorite, although dried cherries are a close second) and a smaller amount of chocolate chips. There's no reason why you can't enjoy a little dark chocolate sweetness with all those other healthy foods!
2. Fresh fruit is always in my carry-on bag. On flights from home I bring along oranges, tangerines, or grapefruit peeled and sectioned in a baggie; or sliced apples or pears; or a couple of plums. On flights heading back home I often pick up fresh fruit salad in the airport. The natural fluids in the fruit help me stay hydrated, and the cool flavor plus healthy vitamins perks me up.
3. Peanut butter is one of my favorite pack-along protein foods. I might bring a peanut butter sandwich, or toast a bagel and add peanut butter in the hotel restaurant before I go to the airport. I always bring a small jar of peanut butter in my luggage for a quick snack with crackers in the hotel room as well.
4. Throw a few energy bars in your carry on luggage, and you can survive sitting on the runway for hours without your energy flagging. I like to bring a variety of flavors so I don't get bored with one taste. One tip: avoid anything chocolate. If it gets hot and sticky in the plane, the chocolate melts and makes a big mess. Remember to ask me about the time I didn't notice the chocolate chips from my energy bar that fell on the seat of the plane....and then I sat in them! Larabars are made from unsweetened fruit and nuts with no added sugars, plus they taste great!
5. I always purchase a bottle of plain water in the airport after I go through security. I know, water isn't a food, but it's essential with meals so I'm going to include it. Yeah, you can ask for water on the plane, but then you get a little plastic cup of water. I like to bring a water bottle so I can sip on it the entire trip, and get a plastic cup of ice if I want cold water. It's easy to get dehydrated while flying and traveling, and the only downside of drinking water is that you become very friendly with the people sitting next to the airplane bathroom!