MSA stands for what?

• A. Minimum Offroute Altitude
• B. Minimum Enroute Altitude
• C. Minimum Crossing Altitude
• D. Minimum Safe Altitude

Answer: (D)

Minimum Safe Altitude is the altitude published on IFR charts to guarantee obstacle clearance within a defined area around a navigation aid. For MSAs, the area is divided into sectors around a VOR or similar aid, and the posted altitude in each sector ensures at least 1000 feet of obstacle clearance (2000 feet in mountainous terrain) within roughly 25 nautical miles of the aid. This provides a safety margin when flying by instruments in the vicinity of the aid, especially if your exact position is uncertain. Keep in mind that MSAs are a sector-based safety cushion, not a route altitude for an entire flight; you’ll still follow other minima like MEA (minimum enroute altitude) or MOCA for enroute planning and MCA for crossing altitudes.