MTR designator digit count

Remote Pilot (Part 107) practice question 21 of 21 on Airspace / Classification. ACS element UA.II.A.K3 · difficulty: standard. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONA remote pilot planning a flight identifies a military training route labeled VR1207. What does the four-digit number tell the pilot about that route?

AOne or more segments of the route lie above 1,500 feet AGL
BThe route is flown under IFR regardless of the weather
CNo segment of the route is above 1,500 feet AGL

Show the answer and explanation

Correct answer: C. No segment of the route is above 1,500 feet AGL

A — incorrect Routes that include one or more segments above 1,500 feet AGL carry three number characters, such as IR206 or VR207, not four.
B — incorrect Operating under IFR regardless of weather conditions describes IR routes; the VR prefix identifies a VFR military training route.
C — correct The study guide states that MTRs with no segment above 1,500 feet AGL are identified by four number characters, such as IR1206 or VR1207.

BACKGROUND

Military training routes (MTRs) are routes used by military aircraft to maintain proficiency in tactical flying, and they are usually established below 10,000 feet MSL for operations at speeds in excess of 250 knots. Routes are identified by a prefix of IR for instrument flight rules (IFR) or VR for visual flight rules (VFR), followed by a number. The number of digits is meaningful: four number characters mean the route has no segment above 1,500 feet AGL, while three number characters mean the route includes one or more segments above 1,500 feet AGL. Because a small unmanned aircraft under 14 CFR part 107 operates at low altitude, a four-digit MTR marks airspace where fast military traffic may be operating down in that same low band. VFR sectional charts depict military training activity such as IR and VR routes along with military operation area (MOA), restricted area, warning area, and alert area information.

STUDY TIP

Memorize the digit rule as "four digits means all low, three digits means some high" and pair it with the prefix meaning (IR for IFR, VR for VFR). Remember that a four-digit route is the one most likely to put fast military traffic at your operating altitude.

KEY POINTS

MTRs are identified by an IR or VR prefix followed by a number.
Four number characters mean no route segment is above 1,500 feet AGL.
Three number characters mean one or more segments are above 1,500 feet AGL.

SOURCES

remote_pilot_study_guide.txt, Chapter 2, "Military Training Routes (MTRs)"

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