A circle-to-land approach is not technically an approach, but a maneuver initiated by a pilot to align the aircraft with the runway for landing when a straight-in landing from an instrument approach is not possible or desirable. At tower-controlled airports, this maneuver is made only after ATC authorization has been obtained and the pilot has established required visual reference to the airport. When either the normal rate of descent or the runway alignment factor of 30° (15° for GPS IAPs) is exceeded, a straight-in minimum is not published and a circling minimum applies. The fact that a straight-in minimum is not published does not preclude pilots from landing straight-in, if they have the active runway in sight and have sufficient time to make a normal approach to landing. Under such conditions and when ATC has cleared them for landing on that runway, pilots are not expected to circle even though only circling minimums are published. A pilot can circle to land if needed when cleared for a straight-in approach. A "straight-in approach" is an instrument approach wherein final approach is begun without first having executed a procedure turn. Such an approach is not necessarily completed with a straight-in landing or made to straight-in minimums.

During a circling approach, three conditions are required before descent from the MDA can occur: 

1. The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers. 

2. The flight visibility is not less than the visibility prescribed in the standard instrument approach being used.

3. At least one of the specific runway visual references for the intended runway is distinctly visible and identifiable to the pilot.

If visual reference is lost while circling to land from an instrument approach, the pilot should make an initial climbing turn toward the landing runway and continue the turn until established on the missed approach course. Since the circling maneuver may be accomplished in more than one direction, different patterns will be required to become established on the prescribed missed approach course, depending on the aircraft position at the time visual reference is lost. Adherence to the procedure will ensure that an aircraft will remain within the circling and missed approach obstacle clearance areas.

In all circling approaches, the circling minimum provides 300 feet of obstacle clearance within the circling approach area. The size of this area depends on the category in which the aircraft operates: 

Category A: 1.3 mile radius

Category B: 1.5 mile radius 

Category C: 1.7 mile radius 

Category D: 2.3 mile radius 

Category E: 4.5 mile radius

Minimums are specified for various aircraft approach categories based on a speed of VREF (if specified), or VREF is not specified, VS0 multiplied by 1.3 at the maximum certificated gross landing weight.

Different aircraft approach categories: 

Category A: Speed less than 91 knots

Category B: Speed 91 knots or more but less than 

121 knots

Category C: Speed 121 knots or more but less 

than 141 knots

Category D: Speed 141 knots or more but less 

than 166 knots

Category E: Speed 166 knots or more

An aircraft can only fit into one approach category. If it is necessary to maneuver at speeds in excess of the upper limit of the speed range for each category, the minimum for the next tier approach category should be used.