Definition
An example designator for a specific Military Training Route (MTR) flown under Instrument Flight Rules (IFR). The 'IR' prefix indicates the route is operated under IFR, and the four-digit number '1206' identifies the specific route. Four-digit MTR numbers (1206) indicate that one or more segments of the route include operations above 1,500 feet AGL. Three-digit MTR numbers indicate the entire route is at or below 1,500 feet AGL.
Plain English
IR1206 is the name of a particular military training route. The 'IR' part means military aircraft fly it using their instruments, and the number tells you it's a route where some sections are flown higher than 1,500 feet above the ground.
Context Anchor
Seen on aeronautical charts and in discussions of Military Training Routes in the Pilot’s Handbook of Aeronautical Knowledge.
Derivation
The 'IR' stands for 'IFR Route,' meaning the military flight is conducted under Instrument Flight Rules. The four-digit number is assigned by the FAA and DoD to identify each specific MTR. The fact that it has four digits (rather than three) is itself meaningful — it tells you the route includes segments above 1,500 feet AGL.
Why Pilots Care
Civilian pilots must know when IR1206 is active to avoid conflicts with high-speed military traffic operating at low altitudes.
Intuition Check
Do not read IR1206 as a radio frequency, airport code, or aircraft model. It is a route name: “IR” identifies the type of military training route, and “1206” identifies the specific route.
Example Sentence 1
While planning the cross-country, the student noticed IR1206 crossed her route and called Flight Service to check whether the MTR would be active during her flight.
Example Sentence 2
Before departure the pilot checked the active hours for IR1206 to ensure safe separation from military traffic.