There is a list of "participating insurance companies" here:
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I may be wrong but I've thought that those are companies waived from Foreign insurance certificate. Cigna is on that list, so guess I've misunderstood. Or someone has. Still cannot understand the reason for the whole certificate...one either has the document stating the coverage of the insurance or one doesn't. Also the requirement of "medical certificate" is ridiculous since it seems to be easier to summon demons than to find a doctor willing to sign that.