Kayak may offer it, but if you try to book that on the Korean Air website you get: "This is based on the regulations of the U.S. Department of Transportation a

Kayak may offer it, but if you try to book that on the Korean Air website you get: "This is based on the regulations of the U.S. Department of Transportation and you cannot make a reservation for an itinerary from the mainland U.S. to Guam (GUM) via a third country" The rule is not that foreign-owned airlines can't fly point-to-point routes between US destinations - Air Canada can't sell SFO→JFK via Toronto, for instance. You may somehow be able to cause something to be ticketed, but that doesn't mean that you'd be able to check in.