IFR restrictions are defined by ceilings or visibility below which values?

• A. < 1000 ft ceiling or < 3 SM vis
• B. < 500 ft ceiling or < 1 SM vis
• C. 1000 - 3000 ft ceiling or 3 - 5 SM vis
• D. > 3000 ft ceiling and 5 SM vis

Answer: (A)

When deciding between VFR and IFR, the boundary is set by weather minimums for ceiling and visibility. If the lowest cloud layer is 1000 feet above the surface or lower, or the prevailing visibility is 3 statute miles or less, the flight is in IFR conditions. The important point is the word “or”—either criterion being below its threshold triggers IFR. So, even with a high ceiling but very low visibility, or with a low ceiling but good visibility, IFR rules apply. The numbers 1000 ft and 3 SM are the standard reference for this boundary in basic understanding, though actual minimums can vary by airspace and operation.