Enroute Academy Controller Knowledge Test (CKT) 1 Practice Exam

When you can’t approve a pilot’s deviation, the proper action is to issue UNABLE and, if time permits, provide a brief reason. This clear verbage communicates that the requested change cannot be granted and explains the constraint so the pilot can adjust their plan or seek an alternative routing while you maintain safe separation. Ignoring the request leaves the pilot without necessary information, and rerouting to an alternate airport or simply increasing separation isn’t the immediate response to a deviation request. Providing the UNABLE with a reason keeps the operation safe and predictable.