The 113th Aerospace Control Alert Detachment of the District of Columbia Air National Guard at JB Andrews, Maryland, passed a major milestone on 9 January 2013, responding to its 4,000th alert event since Operation Noble Eagle began in September 2001. An alert event is counted when the unit's F-16 fighters are alerted to the runway or beyond responding to a possible airborne threat. The 113th ACA, which protects the National Capital Region, is the most active air defense unit in the nation. In 2012, 113th ACA pilots responded to 509 events. Since the terrorist attacks on the US on 11 September 2001, Continental US NORAD Region fighters have responded to more than 5,000 possible air threats and have flown more than 62,500 sorties.
