What is the minimum IFR altitude?

• A. The lowest altitude at which obstacle clearance is assured along a route or segment under standard conditions
• B. The lowest altitude you can descend to during IFR
• C. The highest altitude allowed on IFR flight
• D. The altitude for instrument landing procedures

Answer: (A)

Minimum IFR altitude is the lowest altitude on an IFR route or segment at which you are guaranteed obstacle clearance and reliable navigation signal coverage, assuming standard temperature. This ensures you stay high enough to clear terrain and man-made obstacles while still being able to receive and use your navigation aids to follow the route. In practice, you’ll see this published on en route charts as the altitude that protects you from obstacles and maintains VOR/DME/GPS reception along the path. Temperature deviations can affect true altitude, so in cold conditions the effective protection might require higher altitudes than published. The other statements describe descend limits during IFR, the highest IFR altitude, or altitudes tied to instrument approaches, none of which define the en route minimum safe altitude.