So my grandson taken by his father and didn't tell his mom where they were only to find out the other grandma came to take him to Chicago without permission from the mom. He plans on leaving him in Chicago. So my question is do they need ID hes 3yo

First who's got the custudy of the child ? Second if the child was taken without permission or a notarized letter is a violation of a court stipulation!! My suggestion is call the police and have a police report filed then you have a proof.

Not many 3 year old children carry government issued photo ID.

U need to call local police

I would call local police departments in both cities and let them investigate

I don't think so if it's a local flight? Isn't this a matter for the police?

Not if he was with his Dad, but saw they do ask a couple questions.