Definition
The lowest altitudes prescribed by regulation for IFR flight. They are set to provide adequate terrain and obstacle clearance and, where applicable, acceptable navigation signal coverage. Minimum IFR altitudes include the Minimum En Route Altitude (MEA), Minimum Obstruction Clearance Altitude (MOCA), Minimum Vectoring Altitude (MVA), and the off-route altitudes published on charts (such as OROCA) or established by 14 CFR Part 91 when no specific altitude is published.
Plain English
The lowest altitudes a pilot is allowed to fly when operating under instrument flight rules. They are set high enough to keep the aircraft safely above terrain and obstacles, and high enough for navigation signals to work where required.
Context Anchor
You may see MIA in IFR procedures, air traffic control discussions, and FAA material about minimum altitudes for instrument flying.
Why Pilots Care
Ensures safe terrain and obstacle clearance during instrument flight, reducing the risk of controlled flight into terrain.
Intuition Check
Minimum does not mean the best or most comfortable altitude. It means the lowest altitude allowed for that IFR situation; a higher altitude may still be safer or required.
Example Sentence 1
The pilot reviewed the minimum IFR altitudes for each segment of the route before filing the flight plan.
Example Sentence 2
During the IFR flight, the aircraft maintained the MIA to remain clear of terrain.