Thanks, it was simply the Icelandair legs that concerned me.
For information, I will be transferring to an American carrier for flights inside America. My searches so far indicate that I can save money that way. My flight will be Aberdeen to Keflavik then Washington, then to Cody where I will join my tour group, then from Phoenix to Washington. I intend staying in Washington for some days - perhaps a week - to do the tourism thing, particularly the Smithsonian and hopefully a tour of the White House, then back to Aberdeen. If the prospects for the Northern Lights are good I might stay in Reykjavik for a night or two on the way back.