The US airline industry on Wednesday faced its biggest shake-out in a decade after Delta Air Lines and Northwest Airlines, the third- and fourth-largest carriers by revenue respectively, both filed for bankruptcy.

The bankruptcies after four years of heavy losses and at least 120,000 job losses across the sector are likely to accelerate an industry-wide restructuring around a low-cost model but could raise political pressure on the indebted federal agency that insures workers' pensions.