So long as you have a medical marijuana card issued in the state that you reside and are flying to another state where medical marijuana use is allowed, you should have no trouble possessing such a controlled substance in the second state.The concern that you need to be aware about is that flight across state lines is controlled by federal law and federal law does not recognize the legality of marijuana like some states in this country do. As such, you may have some legal issues under federal law flying in and out of the state you wish to travel to.