United Airlines and Star Alliance carriers have low fares from $742 to $765 from Los Angeles and San Francisco to Muscat, Oman for November 2015 departures. Not as low as the fares used by Brian Cohen of The Gate or Drew and Carrie of Travel is Free when they traveled to Oman earlier this year and blogged about their travels.
I found itineraries with United, Swiss, Lufthansa, Air Canada, Turkish and Flydubai. Skyteam has comparable fares with Delta, KLM and Air France.
San Francisco SFO – MCT Muscat, Oman
November 24 – December 2, 2015
SFO-IAD-DXB (United Airlines)-MCT (Swiss)-DXB (Flydubai)-IAD-SFO (United)
19,410 flight miles, but $643 base fare means 3,215 base miles for United Mileage Plus members.
You can do an all Swiss Airlines itinerary for about $25 more.
KLM/Delta have similar fares and some routings allow an overnight in Amsterdam.