Upvote:-3
As far as I am concerned, Puerto Rico is not in the US and ESTA is only required when travelling to the us... And since you sate your flight is directly to Norway ESTA is completely irrelevant. It would be like requiring a Chinese Visa to fly directly from South Korea to Belgium.
Upvote:2
You will (or might) need an ESTA to enter San Juan by boat, but not to leave San Juan by air.
Upvote:3
No. ESTA is applicable only for travel to US territory.