As I like flying in Alaska, I think I know of quite a few really nice airports, fields and strips.
One of the nicest and biggest (free) airport scenery files available for Alaska is
Anchorage 'Ted Stevens' International (PANC) by William Morgan of FRF Studio's. You already know the FRF quality from their KJFK scenery. But also
Unalaska - Dutch Harbour (PADU) by John Loney is really nice.
Finally, I believe that you should check out the magnificent
Glacier Bay V1 and
Glacier Bay V2, by Holger Sandmann, which includes a very nice rendition of Juneau International amonst other really good (relatively small) airports, which are mostly suited for bush flying. I've seen your 'Tour of St. Maarten' and I think you might be interested in the smaller airfields too ...
On the payware side I can recommend
Tongass Fjords (which includes Sitka, Petersburg and Wrangel Airports) and
Misty Fjords (which includes a rather nice Ketchikan Airport). For both are very good communities like
http://www.tongasswild.com for Tongas Fjords and
http://www.mistymoorings.com for Misty Fjords. Both communities have a wealth of freeware addons for the aforementioned sceneries. FSAddon also has
Harvey & Monroe,
Orcas Island in Washington State and
Wenatchee Skykomish. All of these are exceptionally good.
And - of course - the great
Georender series and
Emma Field by LAGO. The latter has
a few very nice freeware expansions.
A lot of the free scenery requires one or all of the following:
FS Enhancer by LAGO,
RWY12 by Seev Kahn and/or
EZ Scenery by Abacus. Don't forget to get as many libraries for these addon's as you can get!
If you like the smaller airfields, there are around 350 scenery files available for Alaska. Of course it is impossible to list them all here but if you send me an e-mail I can send you an Excel spreadsheet listing all of the scenery files I have installed for Alaska.
And by the way: the ICAO code for Dulles is KIAD. (check out
http://www.airnav.com/airport/KIAD)