One of the great secrets frequent flyers know is that Star Alliance Gold members get access to lounges operated by Star Alliance member airlines when departing on a Star Alliance flight, regardless of class of service traveled.
The only exception is that United’s Gold, Platinum, and 1K members don’t get access to United’s clubs when flying domestically.
Of course Star Alliance Gold members of airlines other than United do get access even to United’s clubs on domestic US flights. That’s why status matches to foreign airlines are so cool, they save you from buying a membership.
Most people think the United club exclusion means United Gold elites don’t get lounge access on domestic trips (unless they’re a United Club member). But that’s wrong.
The trick – that the initiated know but most do not – is that any Star Gold member can access any Star Alliance lounge in the U.S. other than United’s clubs provided they are flying on Star Alliance airlines out of that airport that day and can physically access the terminal where the lounge is located.
United Gold elites and higher and other Star Alliance Gold members get access, for instance, to both the Turkish Airlines lounge and to the Lufthansa Senator lounge at Washington Dulles airport’s B concourse. The B concourse is connected to the terminals used by United inside security. So if you’ve got time to kill at the airport, are a United Gold or higher, you can use those lounges.
Lufthansa also operates a lounge in Detroit between gates D6 and D8 (which is on the way to the United gates). Lufthansa has lounges that are less-usefully located at New York JFK by terminal 1’s gate 3 and Newark by terminal B’s gate 60. There are Swiss and SAS lounges in terminal 5 at Chicago O’Hare.
It’s worth noting, however, that the Singapore Airlines lounge in San Francisco has a reputation for not following Star Alliance rules and denying access to United elites departing the airport on a domestic flight.