Definition
An example designator for a specific Military Training Route (MTR) flown under Instrument Flight Rules (IFR). The 'IR' prefix identifies the route as IFR, and the route number that follows it (in this case 206) is the unique identifier for that particular route. A three- or four-digit number indicates the route is generally flown at or below 1,500 feet AGL.
Plain English
IR206 is the name of one specific military low-altitude training route. The 'IR' part means the route is flown under instrument flight rules, and the number tells you which route it is.
Context Anchor
Seen on aeronautical charts and in route information for Military Training Routes.
Derivation
IR' stands for 'IFR Route.' The number is simply an identifier assigned by the military and FAA. Three- or four-digit numbers were chosen to indicate routes flown at or below 1,500 feet AGL, while one- or two-digit numbers indicate routes that include segments above 1,500 feet AGL.
Why Pilots Care
MTRs like IR206 are used by military aircraft flying at high speeds and low altitudes. Civilian pilots need to recognize these route designators on charts so they can stay aware of where fast-moving military traffic may be operating.
Intuition Check
Do not read IR206 as a radio frequency, airway, or airport code. It is a military training route name.
Example Sentence 1
While planning a cross-country flight, the pilot noted that IR206 crossed her intended route and called Flight Service to check for scheduled military activity.
Example Sentence 2
ATC advised traffic on IR206 and suggested a slight heading change to remain clear.