So that I'm not showing favoritism out of ignorance, help me clear something up...
A couple of weeks after reaching Elite 1 membership on TWA, the gate agents would upgrade me to First Class anytime a seat was available. This was without any reward certificates. The first time it happend, I asked the agent why she did this and she replied, "We like to take care of our best customers".
Is this common on other carriers?
I should also note that after my first flight with TWA, I refused passage on any other carrier regardless of cost or layover. So long as there flew to my destination!