Date: 201512
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: Military Transport
Operator: Military
Operating under: Part 91
Flight plan: VFR
Mission: Training
Flight phase: Initial Approach
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Second aircraft: Medium Large Transport; Low Wing; 2 Turbojet Eng
Reporter organization: Government
Reporter function: Departure; Approach
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Training / Qualification; Situational Awareness
Anomaly: ATC Issue All Types; Airspace Violation All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Contributing factors: Procedure; Airspace Structure; Airport
Primary problem: Airspace Structure

Narrative: I was working all of the airspace. Traffic was light; normal for that time of day. ZZZ was on Runway XX; ZZZ1 on Runway YY. ZZZ1 had two military transports performing multiple traffic pattern runs; both left and right downwind for Runway YY. I had noticed the military transports were occasionally spilling over outside of the ZZZ1 Class D airspace. Shortly after; I accepted two silent releases; one for a Runway XX west departure; the second for a south bound departure which overflies ZZZ1. The military transports appeared to be coming around for another pass; this one on the left downwind for ZZZ1 Runway YY. I displayed the ZZZ1 Class D airspace map on my scope to double check the military transport's positioning.When I observed the first military transport did not appear to be turning base; I asked the TRACON Controller in Charge (CIC) to call ZZZ1 and ensure they turn the military transports away immediately as I had traffic on the roll at ZZZ. At this point the first military transport had not only violated the inner boundary of the ZZZ Class C airspace; but was encroaching on ZZZ Tower airspace and was opposite course with the departing southbound Aircraft Y. The Tower controller; who happened to be the Supervisor on duty; took evasive action and turned Aircraft Y to the west. After review of the FALCON replay; Aircraft X and Aircraft Y came as close as 1.2nm laterally with 100ft vertical.The proximity of ZZZ1 to ZZZ requires the highest level of vigilance in regards to ensuring that aircraft remain within the assigned airspace boundaries. ZZZ1 airspace is adjacent to ZZZ's Class C inner boundary five mile ring. Aircraft in the ZZZ1 traffic pattern routinely approach the airspace boundary. Any extension of the left downwind for Runway YY at ZZZ1 immediately enters ZZZ Class C airspace. In this case; the military transport extended so much it entered ZZZ Tower airspace as well. Runway YY left downwind operations at ZZZ1 appear to be high risk when ZZZ is departing Runway XX and therefore should go under review. The time frame necessary to properly coordinate and even cancel a takeoff clearance for a ZZZ departure; in order to accommodate an extended left downwind for ZZZ1 Runway YY; is very small and has exposed a serious concern in our airspace.




Synopsis: Two military aircraft were in a VFR airport traffic pattern training. They were observed by the TRACON Controller deviating outside the airspace of their traffic pattern and into the Class C airspace of an adjacent airport. The TRACON Controller instructed the Tower Controller to ensure the training aircraft remained in their Tower airspace. An aircraft departed from the Class C airport as one of the training aircraft deviated again towards the departing aircraft's path. The Local Controller working the departing aircraft instructed it to turn west away from the deviating aircraft.