US Air(ways) since (gulp!) 1991.
Did not fly much early on, but did attend a conference or two here and there and vacation here and there. Took me 3 years to earn my first free coach (gulp!) roundtrip. So, off I went to San Fran to see the Grateful Dead. Then I started to fly (domestic only) more for work when I lived in Miami and, at the time US Air was matched up with BA so you could earn status miles on both. I visited a friend in London twice in the same year on off-season $350 r/t tickets to LHR from MIA and the next thing I knew I was checking in at the US Air First Class line and getting an upgrade most of the time. Gee, I kind of like this. And, no I never used any of my miles. Hmmmm, I wonder what this NEXT elite tier is like.... 100% mileage bonus, more upgrades, upgrade 3 days in advance instead of 1.... the rest is history (a very costly $$$ history). Oh, yea, and geography - I live on the US east coast and US Airways flies all over the place from here. Cheers.