Nap-of-the-earth

Nap-of-the-earth (NOE) is a type of very low-altitude flight course used by military aircraft to avoid enemy detection and attack in a high-threat environment. Other, mostly older terms include "contour flying", "ground-hugging", "terrain masking", "flying under the radar" and "hedgehopping".

During NOE flight, geographical features are used as cover, exploiting valleys and folds in the terrain by flying in, rather than over, them. This keeps the aircraft below enemy air defence radar coverage, avoiding being silhouetted against the sky.