Some vegetables are more portable than others are. For snacking on an airplane, think fresh, raw carrot sticks and celery. Vegetables are also one of the few things that will allow you to feel smugly superior to the person in the next seat eating an apple. Carrots contain lots of vitamin A and about as much potassium as an apple (one medium-sized carrot vs. one medium-sized apple) and they're similarly low in fat. Celery gives you vitamins K and C, and, reportedly, might help in lowering blood pressure [source: Rarback]. Want something besides celery and carrots? Try jicama sticks, baby broccoli or cauliflower florets, and bell pepper slices or asparagus spears.
Leaving the nutritional merits of these crunchy, satisfying snacks aside for the moment, what about dip? There you run into an airplane-specific problem. It's not just difficult to pack; the Transportation Security Administration prohibits it, presumably as a part of the general restrictions on liquids and gels.