Minimum Safe Altitude

Minimum safe altitude is the lowest altitude that will provide acceptable obstacle clearance in an area. This general term is used in multiple specific contexts: the minimum safe altitude shown on approach charts for emergency use, the minimum altitudes for certain types of flight operations, and ATC-assigned minimum altitudes in radar environments.

MSA on Approach Charts

Approach charts display a Minimum Safe Altitude (MSA) circle — usually divided into sectors — centred on a specified navaid or waypoint. The MSA provides 1,000 ft clearance above all obstacles within 25 NM (or the sector radius shown). It is for emergency use only — not for normal approaches.

Related Terms

See also: Minimum Sector Altitude, Obstacle Clearance Altitude/Height.