We admit we were thrown by the recent arrival of Pan Am, the first passenger airline to inaugurate regular service at a certain $313 million concrete patch near Mascoutah, Ill. After all, Pan Am is a storied name in aviation -- although its latest incarnation is a mere shadow of the airline that shut down nearly 10 years ago. But it's one thing to buy the name of a dead airline and another to snatch an airline from its deathbed, again and again. You've got to hand it to the folks at Trans World Airlines, our hometown airline, who've weathered more turbulence than most other carriers, unfriendly press coverage, Wall Street's derision -- and still have managed to run a quality passenger airline that in the past year has maintained the top on-time performance in the business. Flown TWA lately? The crews are friendly, the service is comparable to that of other major carriers, and the planes go where they're supposed to. Of course, we began to sweat when the airline's stock drifted to an all-time low in April, but once again, TWA fooled us and bounced back. Wags can offer a host of reasons TWA defies predictions of gloom and doom. Could it be the significant public subsidies city taxpayers gave the airline when it was last on its deathbed? Could it be that it has a virtual lock on the St. Louis market -- and prices its tickets accordingly? Could it be that the airline's balance sheet is too red to allow it to fail or even to be gobbled up in a merger? Nah -- TWA is around because, well, it's the best we got.