We are looking at buying one especially for this trip. in doing a bit of research, it looks like you can use the "battery" only mode (guess airplane mode as you referred to)
you do charge it by plugging into computer ala Ipod, but can buy a charger to plug in the wall. Would probably buy that charger so we can be sure to keep the battery charged.
Wondered if anyone else had brought a Kindle with them, especially with a longer cruise, you don't want to have a suitcase filled with books. My child can read a book or 2 a day!
thanks for all the good info