i never eat much on the plane, we always fly with virgin long haul and there offerings are normally some kind of chicken or beef with mash and vegs, some fruit or choc pot,salad and a roll, they even bring out ice creams mid flight...lol
My son is Autistic and i always request a jacket potato for him with cheese and beans and they accomadte us well and it tastes good so you could ask for this...he had it on his first flight (i think was a crew meal...?he was being fussy and they brought it out.) and now expects it everytime.
Its hardly a normal day reflective of your eating habits, just take snacks with you make sure to drink loads , flying dehydrates you!!
have fun xxx