Well, I am just back from a flight with DS
We are in the UK now!
The food I love to take is snacky food that takes him LOOOOOONG to eat and that he loves.
He must have tried it before (can't give a baby new food on a plane because of the risk of allergic reaction)...
I would go for loads of bicuits, muffins, bananas and some healthy jars just so that you don't feel that bad... finger foods at that stage take ages to eat which is great during a flight because it forces him to chew and swallow which is good during the flight
I find sleep the bigger problem than food though...