Last year was a good one for the airline industry, with U.S. airlines churning out the highest profits in more than a decade. With the exception of American Airlines, every major carrier turned in positive profits for the year.

In the 2011 Airline Quality Rating (AQR) report released on April 4, quality is up as well.

We've compiled a list of the airlines that could stand to improve their customer service, based on the recently released 2011 Airline Quality Rating (AQR) report. The report covers 16 domestic carriers and its methodology factors in several common complaint areas, including mishandled baggage, flight delays and involuntary denied boardings (a.k.a. "getting bumped"). Also note: We've ranked regional airlines separately because of their tendency to score lower.

AQR Score: -1.22

Delta received an AQR score of -1.22, a tremendous improvement from the previous year's -1.73 (which was worst among major airlines). However, Delta had the highest customer complaint rate (2.00 per 100,000 passengers) of all airlines in 2010, including regional carriers. Additionally, Delta placed in the number six spot on Business Insider's "Worst Companies" list. Take note of Delta's baggage fees below, as they can get quite cumbersome if you're checking heavy or large bags.

AQR Score: -1.23

Continental showed improvement in the mishandled baggage and on-time performance categories in 2010 compared with 2009. However, significant setbacks included customer complaints (the rate was up to 1.48 per 100,000 passengers versus 1.00 in 2009) and denied boardings (1.82 bumps per 10,000 passengers versus 1.57). Like Delta, Continental can really hit your wallet if you're checking in some heavy luggage -- check out the baggage fees below.

AQR Score: -1.27

Frontier's AQR score dropped from -1.09 last year to -1.27 on the 2011 AQR Report. While its on-time performance improved somewhat with 81.4 percent of flights arriving on time (up from 78.3 percent in 2009), its customer complaint (1.23 per 100,000 passengers versus .92 the previous year) and mishandled baggage (2.58 incidents per 1,000 passengers versus 2.50) rates took Frontier in the wrong direction.

Overweight/Oversized Bags

AQR Score: -1.28

American Airlines has an AQR score of -1.28, which actually looks pretty good when compared to its regional partner, American Eagle (more on them later). In 2010, AA was fifth worst in total consumer complaints among all airlines surveyed, with 1.44 complaints reported per 100,000 passengers. Business Insider identified AA as the seventh worst company in America and cited several reasons, including high baggage fees and service cutbacks.

AQR Score: -1.31

United had the worst AQR score among major airlines with a -1.31, with customer service as its Achilles' heel. According to the AQR report, United had the second-highest customer complaint rate in 2010 with 1.64 complaints reported per 100,000 passengers. United had the unfortunate distinction of placing second on Business Insider's "The 18 Worst Companies in America" list. High baggage fees haven't helped the company's image.

Please note that the regional airlines typically follow the baggage fee structure of their major airline partners.

AQR Score: -1.28

SkyWest Airlines has several hubs throughout the United States, including Chicago and Los Angeles. SkyWest received a -1.28 AQR score, an improvement over the previous year's -1.57. One area that contributed to this improvement was mishandled baggage, where it averaged 4.72 incidents per 1,000 passengers in 2010 compared to 5.69 in 2009. SkyWest acts as a regional airline for AirTran, Delta Connection and United Express.

AQR Score: -1.53

Mesa Airlines' AQR score dropped slightly in 2010 despite improvements in some key categories. The customer complaint rate was .53 complaints per 100,000 passengers, down from .61 the previous year. Mesa fared much better than the prior year with mishandled baggage (though still performing worse than the industry average). However, Mesa's rate of denied boardings soared from 1.47 per 10,000 passengers in 2009 to 2.55 in 2010. Mesa acts as a regional carrier for United Airlines and US Airways.

AQR Score: -1.56

With a -1.56 AQR score, Comair got the third-worst score among all airlines surveyed for the 2011 Airline Quality Ratings. Mishandled baggage was a major culprit, with an average of 5.28 incidents per 1,000 passengers in 2010. Comair also had the worst on-time performance of all carriers surveyed in 2010, with only 73.1 percent of flights arriving on time. Comair is a regional partner for Delta Connection. Its airport hubs are Cincinnati-Northern Kentucky and JFK airports.

AQR Score: -1.72

Atlantic Southeast received a -1.72 AQR score, which is the second-worst score among all airlines covered in the 2011 Airline Quality Ratings. Atlantic Southeast serves as a regional airline for Delta Connection and United Express with several hubs, including Memphis and Chicago. It had the second-most incidents of mishandled baggage in 2010 (6.71 reports per 1,000 passengers).

AQR Score: -2.82

With a -2.82 AQR score, American Eagle has the unwelcome distinction of having the worst overall score among all national and regional airlines covered for the 2011 Airline Quality Ratings. It also had the most incidents of mishandled baggage (7.15 reports per 1,000 passengers) and the highest rate of involuntary denied boardings (4.02 per 10,000 passengers). American Eagle is the largest regional partner for American Airlines and operates out of a number of hubs, including Chicago and Dallas.