This is my standard approach, usually either a sub or a wrap. I haven't flown much in the last two years, but if UA still sells the snack boxes, I would occasionally buy one of those on the plane. I never bring food from home. For domestic flights, it's pretty rare that I can't plan meals around flights, so my preference would be not to eat on the plane at all. Nice thing about ORD is that my average domestic flight time is about 2.5 hours and pretty much never more than 4.

For long haul, I usually try to find a way into business class (much harder now that I'm not 1K) through purchase or upgrade, but if I can't, I'll buy a couple bags of chips in the airport just in case the meal isn't enough, or isn't edible.