OM stands for what marker in instrument navigation?

• A. Omnidirectional Marker
• B. Origin Marker
• C. Outer Marker
• D. Oblique Marker

Answer: (C)

The concept here is understanding marker beacons on an ILS approach. OM is Outer Marker, a marker beacon along the ILS localizer/glide slope that you encounter farther from the runway. It helps confirm you’re at a defined point on the approach and on the published glide path, typically located about 4 to 7 miles from the runway. In the cockpit, you’d observe the blue marker light and hear the distinctive signal associated with this beacon, distinguishing it from other approach beacons. The other terms listed aren’t used for ILS markers—there are markers on the approach called Inner Marker and Middle Marker, and there isn’t a marker designated as Omnidirectional, Origin, or Oblique.