Answer:
I'm a starchy plant tuber that is one of the most important food crops, cooked and eaten fried, such as french fries.
This is a dead giveaway
It flows out of the soil, It burns you if it boils, And holds us in its coils, More valuable than gold, As black as it is old.
If you are unsure how to use one then just ask a flight attendant.
What Can Fly Without Wings
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?