Try the Clif Mojo Bars

http://www.clifbar.com/food/products_mojo/1238

I carry these in my bag and make sure I eat one about 60% into my flight. I also always eat breakfast. More protein than carbs but you do need some carbs, your brain needs it also.

Water Water water, and I take a Multi-Vitamin, one B-Complex, and every other day take one Calcium supplement.

Long trips I take one baby aspirin prior to starting the day.