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SESK: Stuff Everyone Should Know · sesk.info/drone-mtr-four-digit-route

What does a four-digit military training route number indicate?

It has no segment above 1,500 feet AGL.

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  1. It is closed four days weekly
  2. It has four control towers
  3. No segment is above 1,500 feet AGL ✔

Why: IR and VR routes with four numeric characters have no segment above 1,500 feet AGL. A three-digit route includes at least one segment above that height.

Huh, didn't know that: Military training routes commonly support low-altitude, high-speed training.

The dad joke
Why did the route count its digits? It wanted to stay on the level.
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References

Answer: No segment is above 1,500 feet AGL. IR and VR routes with four numeric characters have no segment above 1,500 feet AGL. A three-digit route includes at least one segment above that height.

  1. FAA Remote Pilot Study Guide www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/remote_pilot_study_guide.pdf
    MTRs with no segment above 1,500 feet AGL are identified by four number characters
    Checked 2026-10-09.

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