Frankly, I can’t see a significant expansion from Guam into the South Pacific or Asia.

The history of Guam as a Hub came out of the US Governments desire to provide air service to the Trust Territories of the Pacific, formed after WW2. This was just after PanAm’s flying boats were deemed inadequate and long before there was the daily conga line of Asia/Pacific flights we have today. Guam has really become a flyover location and if not for Asian tourism and the Island Hopper (a cool name for what used to be called a milk run) it’s just the Military that significantly drives demand from the US.

I simply don’t see it growing or shrinking much since it’s not really worth the extra time for a stopover to Asia or the Pacific if you don’t intend to spend a few days exploring. They can’t even consistently support HKG flights. And if you are seriously considering a visit to someplace like Port Moresby, it’s easily accessible from Australia or New Zealand.

Here is the history of Continental Micronesia, an interesting watch when you have an hour to spare.
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DEN