g.f.:
I don't think any FAR 121 in the US has circling in its Ops Specs; just isn't done in the Land of the ILS. Which is why TERPS is so outdated on circling minima; if the airlines aren't interested, the FAA couldn't care less.
I've heard there a a few commuter carriers that do the training, thus have the Ops Specs authorization.
But, there is a trap (as in "terps are traps"
) in the Ops Specs limitation for the majority of carriers that do not train to circle. They are, nonetheless, permitted to circle when the weather is not less than a reported ceiling of 1,000 feet, and visibility of 3 miles. If the circling MDA is 1,000 feet (HAA) or greater, it's real circling, albeit without the training or qualifcations. And, I am aware of at least one carrier that wrote their Ops Specs to permit circling at the actual MDA (when lower than 1,000 HAA) provided the weather is not less than 1,000-3; their POI signed off on it.
Circling does occur at some airports by 121 operators. And, I suspect, when it occasionally does happen, it may very well be an extremely high risk maneuver.
What usually saves the day is that there is not a critical obstacle right at the TERPs limits, at least not in combination with an excursion.
The aviation political interests (especially air carrier) in the U.S. are, in some ways, the most corrupt in the world. They fought TERPs Change 21 for decades. Now that it has published, they have manage thus far to not have it implemented.
I dread the thought of being a passenger arriving at PHLI on a dark, rainy night when circling is done at 1000-3 to Runway 3. At least now it is left circling only. Until a few years ago it was right circling only, with huge rocks just beyond the tiny little TERPs "protection" areas.