The widespread job losses and plummeting home values that characterized the Great Recession scared many Americans into being more careful with their money. Some consumers have shied away from buying goods they don't really need. Middle-income Americans have started shopping at thrift stores out of financial necessity or to pursue great deals. And people have been reducing their credit card balances. Delta Air Lines, the world's second-largest airline, is the commercial equivalent of a disciplined consumer who only spends money on goods that are important to him or her. Delta, which operates a majority of the flights out of the Minneapolis-St. Paul International Airport, on Wednesday reported a second-quarter net loss of $168 million. Its quarterly operating profit was $586 million, but special charges that included fuel hedge losses pushed Delta into the loss column. One of the more intriguing aspects of Delta's conference call with analysts and reporters wa