Two studies out in the past several days show the flying public’s complicated relationship with Miramar-based Spirit Airlines: While the low-cost carrier is an industry leader in terms of complaints, it also soars above the competition in profitability.

A profitability ranking released Monday by trade publication Airline Weekly shows that Spirit has the highest operating profit margin — 17 percent — of any airline in the country. Globally, only Copa Airlines of Panama outperforms Spirit by that measure. Allegiant Air follows Spirit closely with an operating margin of 16 percent.

Spirit, a major carrier at Fort Lauderdale-Hollywood International Airport that has been in talks with Miami International Airport about starting operations there, built a business model out of offering low base fares and charging for everything from carry-on luggage to boarding passes printed at the airport. The airline also packs more seats onto its planes than its competitors do.

Those strategies keep both profits and complaints high, according to the second report, issued last week by the U.S. Public Interest Research Group Education Fund. The nonprofit consumer advocacy group released an analysis of U.S. Department of Transportation complaint information from 2009 to 2013 that shows Spirit consistently generated the most complaints per 100,000 passengers.

“Each year, Spirit’s passengers were about three times as likely to file a complaint as the second-place airline, and its complaints volume is trending upward over time,” the report said.

In 2009, for example, the number of complaints per 100,000 passengers was 6.75; that had increased to 9.44 by 2013, the report said. Last year, the most complaints about Spirit had to do with flight problems such as delays and cancellations, followed by reservations/ticketing/boarding and baggage.

A Spirit spokeswoman said in an email Monday that the 2013 number was actually 8 complaints per 100,000, which she called “a pretty small number,” and said many of those issues had to do with customers “not fully understanding that we offer unbundled fares that let them control how much they spend.”

“Spirit is committed to delivering the lowest base and total fare to our customers,” spokeswoman Maggie Espin-Christina said. “We are focused on giving our customers a great value every time they fly Spirit.”

She added that Spirit has declared 2014 the “Year of the Customer” and that the airline is working to reduce complaints by educating customers on how to save the most money when they fly Spirit.

Seth Kaplan, managing partner of Airline Weekly, said the two reports show that Spirit customers might be complaining — but they are also flying with the airline.

“I don’t want to accuse people of lying, but sometimes they say one thing and their actions suggest something else,” he said. “Consciously they might really believe they hate Spirit, but a lot of them on some level have decided that they actually do like Spirit because they don’t like paying a lot of money and they are willing to put up with the things they don’t like about Spirit in exchange for low fares.”

Photo Credit: Passengers wait in line at the Spirit Airlines ticket counter at the O'Hare International Airport in Chicago. Frank Polich / Reuters