The type of snacks you choose to bring depends on whether you are flying domestic or international. For instance, if you are flying internationally, you have to watch things like nuts, seeds, or dairy products because some countries do not want you to have them on you when you land. You also have to watch TSA because I once had a TSA agent tell me that if you bring a piece of pie, like a peach or cherry pie with the jelly like filling, they might not let you take it on because the agent may classify it as a "gel".
So in general, you'll want things that are healthier for you. For instance, it is a good idea to pack some source of protein such as crackers and cheese, sliced meat and crackers, or even protein bars. If you pack your own cheese, you can slice it ahead of time and you can choose crackers that do not fall apart easily and leave a mess. If you go for protein bars, check the back to make sure it doesn't have too much sugar or fat and that it won't make tons of crumbs all over.
Think about packing fruit but make sure it is fruit that travels well such as apples, bananas, or grapes. You can slice the apple and place the slices in a ziplock bag while bananas don't need anything done to them. As far as grapes, make sure they are washed before you pack them. I've taken blueberries and placed some in a small container so they were not crushed. The same goes for fruit such as cherries.
On the other hand, if you don't want to mess with fresh fruit, dried fruit is available. It is easy to transport and tastes good. It can also satisfy a sweet tooth. Look at dried dates, mango, apricot, peaches, or whatever you can find. Dried fruit is relatively light and doesn't add a ton of weight.
If you want to take veggies cut into sticks, they are fine but should you want hummus or peanut butter to accompany them, you have to keep this under 3 ounces otherwise the TSA will confiscate them. Just for your information, there is powdered peanut butter, you can add water to to reconstitute it. I'm not saying it is a fantastic product but it does the job if you really like peanut butter and you can reconstitute it once you've gone through security.
Then one can always make small snack sized bags of things like goldfish, graham crackers, cheese-its or other munchy snack. If you use the small snack sized bags, it gives you a nice sized portion but if you are traveling with children, the small snack sized bags allow each child to have their own serving and they don't have to share. You can package the small bags in one larger quart bag to keep them together.
There is on law that says you can't take a sandwich with you for something more solid. The thing to remember through all this is that whatever you take, it needs to last for several hours and can be eaten safely then. This is important because you have to take into account the time between when you put the snacks together and when the flight leaves the ground.
The most important consideration when bringing snacks with you is to make sure you decide what you want to bring ahead of time so you have time to shop and prepare it. Let me know what you think, I'd love to hear. Have a great day.