And the Airline With the Most Complaints Is... ...Delta. Overall, complaints about US airlines rocketed 28% last year By Mark Russell, Newser Staff Posted Apr 4, 2011 3:43 AM CDT 5 comments Comments Delta Air Lines topped this year's list of passenger complains, according to the Department of Transportation. (Getty Images) (Newser) – If you think flying has gotten worse lately, you're not alone. Airline complaints soared an astounding 28% last year. Oddly, though, actual data reveals that planes improved their performance in a number of areas, with fewer lost bags and bumped passengers, and more on-time arrivals. A co-author of the Transportation Department report speculates that the complaints are due to an increasing number of travelers and fewer flights and seats. Flights tend now to be packed, making it tougher to rebook. "Even though airlines are vocal about saying they want to please the customer, when it comes right down to it, they're going to make money first," she tells AP. The report tallies problems in four categories—on-time arrivals, mishandled baggage, denied boardings, general complaints. At the top of the Department of Transportation's list of complaints per 100,000 passengers: Delta Airlines, 2 per 100,000 United, 1.64 US Airways, 1.53 Continental, 1.48 American, 1.44 The best of the bunch? Southwest, with just 0.27 complaints per 100,000 passengers. For the full list, see the AP story.