Is there a addon scenery for Alaska anyone would recommend?TKS

For an overall enhancement, look at Ultimate Alaska. For a smaller but more detailed region, look at Orbx's Pacific Fjords. You might want to add Tongass Fjords to the last one (the work together perfectly well: the people of Tongass Fjords worked on Pacific Fjords later on).

UTX Alaska does all of Alaska, from Ketchikan to Barrow. It's very good, if a bit frame-rate heavy in Anchorage. In my opinion, TongassX is the most beautifully rendered with environmental sound and lots of interesting AI ships and planes. It is the smallest area, about 80,000 square miles in the middle of the Alaskan Panhandle. Pacific Fjords is the newest, and it is superb. It only does a small portion of the bottom tip of the panhandle, starting around Thorne Bay, but then it extends down through all of British Columbia to Vancouver. The Ketchikan and Prince Rupert done by Pacific Fjords is worth the price of the package in my opinion, but they don't stop there. They literally improved every airstrip in the coverage area. It's impressive. You have to fly Pacific Fjords to really appreciate how much airport work they actually did, and of course, the terrain modeling is as excellent as TongassX and PNW Blue.

I use Ultimate Alaska which has completely changed it for me, well worth the $$$..... Frame rates seem to be ok, although I have not tried to use the Mustang with it yet !!G

Keep in mind that Ultimate Alaska does allow you to independently lower scenery complexity in many different regions/cities. This another big plus.