They were a short lived commuter airline belonging to Reno Air. (There's better wording for that but I can't think of it right now) They only operated the Jetstream 31's. I believe they had 6 or 7. IIRC, they were in operation around 1995. As for where they flew, I would assume that they flew to Reno (the hub of their mainline) and I know they flew to Arcata-Eureka, Calif. I would also assume that they flew to smaller cities around the west coast of the US.
Hope this helps and I'm pretty sure someone around here can expand on my limited knowledge.
Reno Air Express fed the Reno Air and AA flights at SJC. They also flew to Klamath Falls, OR. A friend of mine was a pilot for Reno Air Express until they went belly-up. I flew on them from SJC to MRY and back.