[JURIST] Delta Airlines [corporate website] and Northwest Airlines [corporate website], the third and fourth largest US air carriers, both filed for Chapter 11 bankruptcy protection [SEC backgrounder] Wednesday. The filings highlighted the financial distress of the airline industry, particularly after spiking oil prices in Hurricane Katrina's wake, and the two airlines are expected to use bankruptcy protection to cut labor and pension costs. Analysts said both companies needed to complete restructuring to compete with other companies such as USAir, which had already filed for bankruptcy [JURIST report]. Some have also said Northwest is likely to gain concessions through bankruptcy that it was unable to obtain in contentious labor negotiations with its mechanics [JURIST report]. Read the bankruptcy filings from both companies [Delta and Northwest; PDF text], as well as the Delta news release and Northwest news release. Delta has legal information available on its bankruptcy proceedings. Reuters has more.