Dallas-Fort Worth-based American Airlines has ranked dead last in customer service in the annual Middle Seat analysis of major domestic carriers.

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United Airlines got sacked as well, showing that mergers can create big customer woes. United and Continental Airlines, when combined, scored almost as poorly as American.

The best-performing carrier last year was Alaska Airlines, the smallest among the seven major U.S. airlines. And in a surprise showing, Delta Air Lines scored a big turnaround, placing second in 2011 compared with ninth in 2010.