Submit A Tip OSI investigates a wide variety of serious offenses - espionage, terrorism, crimes against property, violence against people, larceny, computer hacking, acquisition fraud, drug use and distribution, financial misdeeds, military desertion, corruption of the contracting process, and any other illegal activity that undermines the mission of the U.S. Air Force or the Department of Defense. OSI units are located at most Air Force bases wordwide. If you need to contact OSI, either to provide a tip or share a concern, consult your base phone book or call your base operator for the telephone number of your base's OSI unit. If you do not have a base telephone book and don't know the number to the base operator, call toll free 1-877-246-1453 for the phone number of the OSI unit nearest you. Or if you prefer, send us an e-mail by clicking: email@example.com.