I always bring my own snacks when flying. You just never know what/if anything the airline will serve and it may not be anything you like. Some flights offer food for an extra charge. I have never had any issues going through security with various snacks. If flying a long distance, it is good planning to bring your own snacks and/or purchase something at the airport before boarding your flight. You can typically find salads/sandwiches being sold at various places within the terminal. I would purchase your beverage after you go through security to avoid any issues with the various restrictions on liquids.