A long car ride or a flight
Pack more of the familiar food than you think you need. Delays make new food a poor bet.
Pack the yes, and extra
Offer small pieces while they are sitting, not walking the aisle with a mouthful. Keep the messy new foods for home.
Bread if wheat is fine, soft fruit, or another food they have eaten many times. More than one portion.
Delays
A delayed flight is not the day to introduce lentils. The familiar food is the plan, even if you are bored of it.
If the only airport food clashes with an allergy, skip it. Hungry and safe beats a guess.
Chewing in transit
Stay with them while they eat. Round, hard foods stay in the bag you do not open.
When you arrive, the first meal can still be the same familiar food. Home routines can wait a day.
A sentence you can say
“This is the food from home.”