Lost luggage and rude attendants may make you want to scream. Here are the U.S. airlines that people complained about the most.

(AirTran)

When Andrew Schrage discovered that his seatback TV wasn’t working on his JetBlue flight from Chicago to Boston, he didn’t wait until he landed to complain to the airline. Schrage, an editor at the website MoneyCrashers.com, tweeted @JetBlue before the plane took off, and the airline responded—with a $50 voucher.

Twitter may be changing how we complain to the airlines, but there’s still a lot to complain about. According to the latest Department of Transportation (DOT) report, the agency received nearly 3,600 complaints about airlines from January to June, 2011.

That’s a lot of complaints, even if it is an improvement from the nearly 4,000 received over the same period last year. Not surprisingly, complaints about flight delays and cancellations, rude or incompetent service, and baggage handling led the list.

But what these stats don’t tell you is that legions of consumers are now voicing their complaints directly with the airlines via Twitter. And the airlines—or at least some of them—are listening, responding, and in some cases being proactive and fixing the issues.

Stephanie Dressler, a senior associate at Manhattan-based Montieth & Company, missed her Delta flight to Miami in August 2011 because of an exceptionally slow-moving check-in line at New York’s JFK. So she tweeted pictures of the line to her followers. By the time she arrived in Miami, Delta had apologized to her via Twitter, and on her way home she was upgraded to Delta priority—and coveted exit-row seats.

Clearly, it’s faster to broadcast a complaint in 140 characters or less than to call customer service or log a complaint with the DOT. But not all airlines are listening—some, like Skywest, have Twitter pages that are mere bookmarks. Others, like American Airlines, have eight rotating community managers on Twitter and receive 30,000 tweets per month, according to the airline’s social media communications director, Jonathan Pierce.

Of course, anyone can tweet anything; lodging an official complaint with the DOT means you have a serious gripe. Here are the U.S. airlines the DOT says have had the most—and least—complaints.

No. 16 Southwest Airlines

(Bryan Correira)

.33 complaints per 100,000 passengers

For an airline that moves nearly 10 million passengers per month, Southwest Airlines gets surprisingly few complaints, leading the pack and claiming the title of America's least-complained-about airline.

No. 15 Alaska Airlines

(Don Wilson/Courtesy of Port of Seattle)

.49 complaints per 100,000 passengers

Alaska may have had only 42 complaints this year, but it's still more than last year. Tweet @AlaskaAir when something goes wrong, and chances are you’ll get a faster response than you would by calling, e-mailing, or dealing with customer service at the counter. Its modest following of less than 50,000 will likely grow fast this year.

No. 14 Mesa Airlines

(Ryan Tidwell)

.58 complaints per 100,000 passengers

This regional carrier for Delta, United, and US Airways had the fewest raw number of complaints over the first six months of this year: 25. That’s pretty remarkable, as is its consistency from last year, when they had 24 complaints over the same period of time.

No. 13 AirTran Airways

(AirTran)

.63 complaints per 100,000 passengers

There’s no question that AirTran’s ranking has improved—it has cut its number of complaints in half. But social media has nothing to do with keeping its customers happy; its Twitter presence is nothing more than a placeholder.

No. 12 Frontier Airlines

(Bryan Correira)

.66 complaints per 100,000 passengers

Frontier has begun to be more interactive at @FlyFrontier with its social media–savvy fliers. Maybe that helped push its official complaint rate down from 1.23 over the first six months of 2010.

No. 11 Hawaiian Airlines

(Justin Sinclair)

.73 complaints per 100,000 passengers

With just 31 complaints in the first six months of 2011, the Aloha State’s carrier has improved from the same period last year, when it had 39. And since they've carried more passengers in 2011, Hawaiian's complaint rate has dropped as well.

No. 10 Skywest Airlines

(Bryan Correira)

.77 complaints per 100,000 passengers

The largest independently owned regional airline boasts a low complaint rate even though it flew almost 12 million passengers over the first six months of 2011.

No. 9 Atlantic Southeast Airlines

(Bryan Correira)

.96 complaints per 100,000 passengers

Atlantic Southeast will merge with ExpressJet later this year. Ideally, the newly formed airline will have a Twitter presence, because this airline, which operates close to 1,000 flights every day in the U.S., Canada, and the Caribbean, does not.

No. 8 ExpressJet Airlines

(Marc Vander Maas)

1.01 complaints per 100,000 passengers

Express Jet has slipped from a rate of .70 last year, and its Twitter presence is an anemic placeholder. Let’s hope that when it merges with Atlantic Southeast later this year, a more dynamic social media presence will be part of the business plan.

No. 7 JetBlue Airways

(Bryan Correira)

1.07 complaints per 100,000 passengers

When JetBlue got on the Twitter bandwagon in the spring of 2007—one of the first big brands to jump in—its business plan was that it wanted to help customers. And according to the DOT, there are enough complaints to keep its customer-service folks busy.

See the full list of the most complained about airlines at Travel + Leisure.com