My ex and I share joint legal custody. She wants to travel out of state with our 3 year old. Is she legally obligated to provide me with flight documentation, place where they will stay & phone number?
This depends on what, if anything, is written in the parenting plan. If there is no provision addressing it, she may not have to provide you with this information. She should provide it for legal reasons, but most importantly for the child's safety.
For example, if the child needed emergency medical care and the mother was unavailable (injured or unable to give consent), you could authorize the medical care.